This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
What is the sustained transfer rate for a 15000RPM Ultra320 SCSI drive w avg seek time of 3.3ms? is it still 320MB/s? for example an STA150 drive at 7500 RPM w avg seek time of 8.5 ms (16MB cache) has a sustained transfer rate of 64-35 MB/s & burst transfer rate of 150MB/s. -- Ario 12:34, 13 June 2007 ( 24.2.143.239 16:37, 13 June 2007 (UTC))
Fiber Channel is not an alternative spelling of Fibre Channel.
The concepts relevant only to SCSI Parallel Interface should be separated from the article on SCSI proper. Although SCSI-1 and SCSI-2 include SPI as a central part of the protocol, SCSI-3 has completely split the framework into separate layers. -- Cy jvb 20:20, 2 February 2006 (UTC)
Dis iz a good suggestion so I have split out the SPI content and created a new page called
Parallel SCSI.
Neilm
12:43, 7 February 2006 (UTC)
"SCSI is pronounced "scuzzy" when spoken aloud"... Isn't this a bit pleonastic? -- Edcolins 11:51, Oct 28, 2004 (UTC)
"while occasional attempts to promulgate the more flattering pronunciation "sexy" have never succeeded." Nowadays we're trying to get it to be pronounced "sucksy" ;) -- 148.84.19.92 15:25, 9 Mar 2005 (UTC)
The article says that PATAPI is SCSI over IDE. Isn't this a misnomer? As I recall, parallel ATA is not the only form of IDE, though PATAPI is, of course, over parallel ata.
good article, Mac users in particular grew up on SCSI and SCSI peripherals
How about some pics of the typical fat cables and giant terminators that people remember:
http://images.google.com/images?q=scsi&hl=en&lr=&sa=N&tab=wi
Also what about the SCSI logo ?
http://images.google.com/images?hl=en&lr=&q=scsi+logo&btnG=Search
I agree that this article needs some pictures. Anyone willing to take some? 203.208.80.13 00:51, 14 September 2005 (UTC)
hasn't Apple totally stopped using SCSI ???
Hasn't sun totally had sales of SCSI equipped systems plummet ?
Isnt sales of SCSI hardware now limitted to maintainance (including any strictly run enterprise that has SCSI as standard, so any new hardware must meet the old standard ...one would think that if they made the choice of standards now, they might chose SATA over SCSI .. ) and "main frames" situation, eg fibre channel for connecting 50 scsi devices to the 30 cpu supercomputer. —The preceding unsigned comment was added by 203.82.182.242 ( talk) 02:31, 17 January 2007 (UTC).
This article only seems to talk about devices...as far as I know, in the Linux kernel (for 2.6 at least), firewire IEEE1394 / USB storage devices / Ipod's, etc. they also use the SCSI protocol to communicate to the kernel. Any elaboration on this? -- Natalinasmpf 02:27, 19 Apr 2005 (UTC)
June 22, 2005:
The article should mention "packetized" SCSI that was introduced with Ultra-320. IBM preferred the term "information units" over "packets". I think this was around 2002 or early 2003.
Also, the "Ultra" designations were promoted by the SCSI Trade Association but not used in the ANSI standards. After SCSI-2, the physical interface standard was separated from the logical layers, and became SPI (for SCSI Parallel Interface) and went through generations SPI-1, SPI-2, SPI-3, SPI-4 and SPI-5. STA wanted marketing-oriented nomenclature that reflected the actual maximum data transfer rate of the bus. Note that the SPI acronym can easily cause confusion with other standards.
I don't think "All SCSI standards have been modular, defining various capabilities which manufacturers can include or not" is true of SCSI-1 or SCSI-2, which were monolithic specifications, unless "modular" means something different from what I take it to mean.
The description of the termination network is inside out and backwards. Passive termination uses 2 resisters to TermPwr and ground. Active termination uses 1 resistor to a regulated 3.3 volt source. Differential is 2 lines that are each terminated. In single ended, the other line is a ground. The active termination uses less power and therefore uses a smaller resistance that more closely matches the cable impedance. The tutorial that is already link to has it right < http://www.scsita.org/aboutscsi/SCSI_Termination_Tutorial.html>. It should also be mentioned that the term power fuses have mostly been replaced by a current limiting device. ~ Dan Oetting 136.177.111.33 00:32, 5 November 2005 (UTC)
Thanks. I got that wrong so I have now corrected it. neilm, 5 November 2005.
It's been a long time since I used SCSI. What is used now in servers? Isn't some form of IDE used now? -- Gbleem 16:13, 8 November 2005 (UTC)
In a read or write command block is the data transfer length in bytes or LBAs?
JimT
Always LBAs. See the SCSI Read Commands article for more info.
neilm
Note that Read/Write Long have a byte count in their CDBs. —Preceding unsigned comment added by 195.212.29.92 ( talk) 14:58, 5 January 2009 (UTC)
I miss the description of various SCSI connectors.
xerces8 -- 213.253.102.145 12:31, 16 January 2006 (UTC)
I have added a new page called SCSI connector
neilm 19 January 2006
2 Gbit isn't a clockspeed. In fact it's not a measure of speed at all. It's an amount of data. Clockspeed is measured in Hertz, and ONLY Hertz.
I think it should be made more clear what speeds the different SCSIs run at. Most transfer rates are defined as bits per second (bps) where as what is described here (Bps) which i have come to associate as Bytes per second. This does not, how ever translate over well when comparing transfer speeds.
So either the MB/s needs to be changed over to Mb/s or a subtle hint needs to be added to the text. Is this reasonable?
yet another Matt 14:30, 22 March 2006 (UTC)
What are the device size limits in SCSI ? This subject is always popular with ATA :-) Isn't there a limit at 2 TB (2^32 x 512 byte sectors) ?
- Actually, the new version of SBC supports 64x512 byte sectors, but sometimes the initiator or the OS doesn't support such big disk driver. —Preceding
unsigned comment added by
65.113.40.1 (
talk)
07:38, 10 September 2008 (UTC)
xerces8
--
213.253.102.145
11:00, 24 April 2006 (UTC)
There's nothing about "parallel port SCSI"... I gather it was used for a great many scanners and external disk drives, but beyond that, I don't know much about it. Also, I've seen ATAPI being described as partly based on SCSI, but I'm not sure whether to believe that. -- StuartBrady ( Talk) 14:34, 10 July 2006 (UTC)
The article states "You can attach both narrow and wide SCSI devices to the same parallel bus. To do this, you must put all the narrow SCSI devices at one end and all the wide SCSI devices at the other end, and terminate the high half of the bus in between (because the high half of the bus ends with the last wide SCSI device). "
According to Adaptec, a 68-to-50 pin adapter can be used to put a narrow device on a wide cable, and the high 9 part of the wide cable does not have to be terminated at that point. See Adaptec's KB answer ID 9, "Procedure for connecting both narrow and wide devices to a wide Adaptec SCSI card", in particular the description of the "Adaptec Internal Converter (ACK-68P-50P-IU)". Or are they wrong? Jeh 18:13, 3 August 2006 (UTC)
You can connect a narrow device in the middle of a wide bus.
You can connect a narrow cable to a wide bus, but you must terminate the high data lines at the point of connection between narrow and wide ...
Wide SCSI cards have which have a narrow cable connector usually have a way to terminate only the high data lines at the card. At the other end of the narrrow cable, you need to terminate (in the normal way for narrow), which can only terminate the low (narrow ) data lines ..
And at the other end of the wide cable, you need to terminate in the normal way for wide.
i noticed that on the table at the SSA row the Clock speed goes from Mhz to Mbit. to me that dont seem like it should be Mbit, seeing how it is a clock speed not a transfer rate.
longbow 17:58, 27 Sept 2006 (EST)
As its serial , which means one bit at a time, which means Mbit=MHz.
H for Mr Hertz. Its a name, so its capitalised.
This infobox really does not properly summarize the SCSI protocol suite, so I have removed it.
You could probably add this infobox to the SCSI_Parallel_Interface article, but you need to perform some fact checking first. -- Cy jvb 13:38, 11 October 2006 (UTC)
Consider me ignorant, but where and when is this possible? :: Colin Keigher ( Talk) 05:35, 21 December 2006 (UTC)
http://www.fibrechannel.org/OVERVIEW/topology.html Its very expensive, but it is technically a SCSI system that runs quite a long distance ... :)
In practical terms, its rare fibrechannel system, that is for mainframes, and outside of the scope of standard SCSI
FYI, I'm starting a major overhaul of this article. My goals include: make it easier to navigate; move the focus from SPI to the entire SCSI suite; add citations (to the actual T10 draft standards, when possible); add explanations or links for the tech terms; move individual SPI standard levels out of section headings and into a table, section, or article of their own. While I'm doing this, I may checkpoint with the organization somewhat less perfect than it could be. I may leave it for a day or four while I do things like work or sleep. But I will come back to it, and hopefuly quickly. I just wanted to let people I have a plan, and I'm not just chewing up the article for the heck of it. I'll try and note major progress here. Suggestions, comments, commendations, condemnations, etc., are welcome. — DragonHawk ( talk) 05:27, 17 January 2007 (UTC)
FYI, my own notes on this are at: User:DragonHawk/SCSI — DragonHawk ( talk) 23:47, 28 January 2007 (UTC)
availability of largest hard drives SATA drives: 800 gigabytes, reasonable price SCSI drives: 300 gigabytes, hideous price
Um, non-fibre scsi is dead. Perhaps mainframes will continue to use it, perhaps IBM will order or utilise SATA attached SCSI enclosures, putting SATA drives onto a SCSI bus..
Forgive me for being blunt, but you are just throwing wild speculation into the article (evidenced by your choice of words - probably, indicates, etc.). Your additions are based on a very narrow data point and obviously biased criteria. If you want to comment on the predominance of SATA-interfaced HDDs in the consumer market opposed to SPI-interfaced HDDs, then be my guest. Capacity and price would be obvious factors in the consumer market. You can even comment on the trend towards the cost-effective use of SATA HDDs in SPI/Fibre Channel RAID enclosures for the SMB. What you cannot do is unilaterally proclaim the death of a product (also insinuating the failure of a transport protocol) merely because you do not see a consumer mass-market appeal. There is plenty of information to cite to the contrary.
I'm going to withhold the unleashing of a revert war since in-depth discussion about SCSI HDDs is too SPI-specific anyway. Hopefully DragonHawk's overhaul will set the focus correctly on the protocol suite. Cy jvb 15:31, 18 January 2007 (UTC)
I agree. I am completely bemused by both the substance and the aggressive tone of this whole "controversy". I bought a small HP SCSI based server for £500 only a few months ago. Sure, SATA is more common now but there is no justification for pronouncing SCSI dead for hard drives, never mind for other peripheral types. While I don't like edit warring, I also don't like nonsense being left in the article either. I hope it will be corrected soon as part of the overhaul. -- DanielRigal 11:54, 19 January 2007 (UTC)
We just ordered a bunch of servers from Dell and ended up specifying 15k SAS drives because we need performance, not capacity. So, SCSI is most definitely not dead. Parallel SCSI is close, though. LTO-4 is probably going to be the last tape generation with parallel SCSI. Everybody *hates* SCSI-320, it's so marginal, and SAS is coming down in cost. Ralf-Peter 02:07, 12 March 2007 (UTC)
While I think that an IPA rendering would be lovely, I don't think we should have such a big ugly box on the article. What the heck is up with that anyway? I can hardly think of any article for which the most significant feature on first loading the page should be "Hey, we need IPA for this"; tons of things need or could use IPA, but unlike NPOV and Source Cite notices, I hardly see it as critical to paste a giant warning on. crappy template; where do we go to gripe about it? On the discuss page, a label like that would be ok as a sort of To-Do reminder. (Really, I think discuss pages should be supplemented by a bug tracking system so issues with pages could be neatly categorized, discussed, and resolved). Anyway, there should be a pronunciation section explaining the whole sassy/sexy/scuzzy thing; useful both to non-native/fluent english speakers and people interested in hilarious marketing debacles. But please talk about it here instead of edging towards revert battle. -- Akb4 09:43, 8 March 2007 (UTC)
Hi I have a technical question about scsi write which, if answered, should help improve the description of that command.
SCSI Write, all variants, specify a LBA into a LUN where the data is to be written. There is also a transfer length. presumably the data from a buffer is written to the start of a the specified LBA for the number of bytes in the transfer length. That in itself would be a useful explanation to have on the scsi write page.
however, what happens if the desire is to write, say, 1 byte at offset 10 inside of some LBA? The command does not seem to handle this sort of addressing. Certainly a user can modify a single byte of a file, say in C code.
Under the covers, does this sort of write involve a read to pull in the full 512 byte block, then the one byte is modified, followed by a write? I know this is a bit beyond the low level scsi protocol, which may just say you cant write a single byte, but isnt that what has to be done?
Kdohm 22:19, 29 March 2007 (UTC)
Yup - such is the nature of block addressing. See the SCSI Block Commands document (www.t10.org) for info on Write commands for block devices (disk). Note that for SBC, the transfer length is specified by the number of logical blocks, not bytes.
I think that you can use variable block mode to write a single byte with tape - at least it's valid as far as the command definition states (in this case, the transfer length is specified in bytes). Whether or not the device supports it is another question. Tape also supports relative read/writes depending on the current position of the tape. -- Cy jvb 01:54, 30 March 2007 (UTC)
I'm snipping this
pending a citation. Interesting if true, but we don't need a "some say" / "at some point" assertion in the article.
Along the same lines, long ago, in the heyday of Digital, when RT 128 in Massachusetts was a center of minicomputer development, SCSI was pronounced "sexy." I have no idea how or where ths could be verified, however. Cuvtixo 14:33, 21 August 2007 (UTC)
Vendors tried hard to promote the "sexy" pronunciation against the users seeming preference for "scuzzy". It didn't take. I remember meetings when we were switching from SASI controllers and drives to SCSI --- they'd say only "sexy" and we'd say only "scuzzy", though we were all talking about the same equipment: 5-20MB drives and controllers. ISC PB ( talk) 02:54, 19 November 2008 (UTC)
Does anyone have references as to when different commands were introduced like read(6), read(10), read(16). Which sets the absolute limit on how large discs that can be handled in practice (re ata 48bit mess). Electron9 04:49, 26 July 2007 (UTC)
One: BOTH of you are in violation of WP:3RR. Please allow a cooling off period.
Two: I personally find Tom94022's additional text: begs questions; answers no questions anyone was asking; is misleadingly specific (e.g. not every low level interface to which SCSI interfaced was ST506); incorrect factually (there is nothing as simple as a "bit serial" data stream in the ST506 interface); and poorly worded ("sectors (blocks) of bytes of data"). Apologies, Tom, but that's how I see it. Exactly what are you conveying here, and why does it need to be added to an article on SCSI, which long ago stopped being a bridge -- or an interface -- to another, older interface? Jeh ( talk) 07:26, 31 January 2008 (UTC)
The questionable sentence:
was added by by Bergert (Talk | contribs) at 06:09 on 30 January 2007 and has survived unedited for one year. You may think it is TMI but he did not and I do not, nor has anyone else for one year. Nor do I understand both of your continued and unexplained refusal to accept SASI as part of the history of SCSI - initially the major difference was the name. The only question on the table is what version we return to while we work out the dispute. So I am going back toward the original version but with some of what I believe to be obvious errors corrected. Since we are under WP:3RR policy, i believe it to be a violation if either of you then make any substantive deletions. Tom94022 ( talk) 20:14, 1 February 2008 (UTC)
Subsequent to the above posting IL2BA completely reverted three edits back to his singular version. I consider this to be a gross violation of the WP:3RR policy and have so reported it. It is particularly disappointing that he went as far as to suppress a correction (with reference) to the SASI announcement date, 1979 was not correct, but I guess accuracy doesn't matter in his zeal to own the page. Tom94022 ( talk) 23:01, 1 February 2008 (UTC)
Subsequent to the above posting IL2BA again completely reverted the three edits back to his singular version without any talk at all. Is he even bothering to read the edits? It is clear from a deleted reference that SASI was introduced in 1981 but he continues to revert to 1979 - is there some basis to his reversion other than he doesn't want it changed? It is clear from a deleted reference that SASI and SCSI-1 are the same thing (actually SASI is a compliant subset of SCSI-1)! Isn't this relevant and doesn't it rebut any contention that somehow SASI should be on a different page? It turns out because of my inexperience, my first posting at the Wikipedia:Administrators' noticeboard/3RR 3RR Administrators Noticeboard was not formatted properly and no action was taken, so I have resubmitted my request in what I hope is an appropriate form. Tom94022 ( talk) 07:10, 3 February 2008 (UTC)
((RFCsci | section=SASI as a part of SCSI History !! How much SASI history is relevant to SCSI !! time=19:00, 3 February 2008 (UTC)}}
It has been suggested that information about SASI in the SCSI history section is TMI (too much information) and on such a basis a number of edits have been disputed and continuously reverted. 216.103.87.80 ( talk) 19:00, 3 February 2008 (UTC)
Regarding the one remaining, second dispute, I am restating it below
I'm not wishing to throw gasoline on any fires, but I suspect that the less-than-exact use of the term 'analog' when referring to ST-506 bit-serial MFM signalling isn't entirely inaccurate, if you use it to mean non-digital. Where 'digital' would imply some sort of fixed clock or framing type of system such as RS-232 has. ST-506 didn't, and was merely a faster form of the common floppy interface at the time, where the bit serial stream was wobbly and about as raw as could be had. I don't think there was much more on the drive than the usual head amplifier, one that used differential signalling for the hard disks. The required clock/data separator (for reading) was the hard part! I don't know if there is a term suitable for use between analog (obvious) and what is commonly thought of as a digital interface. ISC PB ( talk) 03:11, 19 November 2008 (UTC)
I struck out the malformed RFC at the beginning of this section. Since there have been no substantive comments proposing the deletion of the SASI material from the article I am going to delete the dispute tag from the History section. Tom94022 ( talk) 18:10, 9 February 2009 (UTC)
SCSI is a peripheral interface: up to 8 or 16 devices can be attached to a single bus.
It appears that SATA and SAS now own the hard drive market, and parallel SCSI is nearly obsolete.
Looking around on big-name drive manufacturer websites, I cannot find any information about current parallel SCSI drives bigger than 300 gigabytes, and that drive size has been available for a couple years now. Meanwhile there are many SAS drives over 300 gigs:
Are any new parallel SCSI drives still being manufactured? DMahalko ( talk) 08:20, 26 October 2009 (UTC)
In the server marketplace the fastest drives are the most expensive, and pushed as being the "enterprise class" models. However, if you have a 300 gb 15000 RPM drive, and a 600 gb 7200 RPM drive, both with the same number of platters, is the 15000 RPM really faster? Or is the performance going to be about equal?
Perpendicular recording allows a higher sector density per cylinder, so a 7200 RPM drive with twice the sectors per track of the 15000 RPM drive should apparently perform equally.
It would appear that what Seagate calls their "enterprise class nearline storage" 2 TB 7200 RPM SAS, will probably have performance at least equal to, or exceeding the abilities of their 600 gb 15000 RPM drives. Since the 2 TB drive has about 3 times the cylinder data density of the 600 gig drive, and it appears that it may perform as well as a 21,600 RPM enterprise class drive.
DMahalko ( talk) 08:28, 26 October 2009 (UTC)
I'm looking at the Parallel SCSI table in the article and am a bit confused over a couple of the maximum length entries. Both "Fast SCSI" and "Fast-Wide SCSI" have a maximum single-ended length of "1.5–3 m". I believe this should simply be "3 m".
I recognize that both "Ultra SCSI" and "Ultra Wide SCSI" have max lengths that vary between 1.5 meters and 3 meters based on the number of devices connected to the bus, but have been unable to find any such reference for Fast SCSI.
Unfortunately I don't have access to the actual SCSI specifications. Can anyone verify whether or not the article is correct?
ChadCloman ( talk) 05:34, 19 March 2010 (UTC)
"U320" redirects to the SCSI page. However, there is no mention of "U320" in the article, so the meaning of the term and the purpose of the redirect both remain obscure. 207.188.235.142 ( talk) 19:03, 3 June 2011 (UTC)
It would be useful to have the standard diamond logo in this article, to help in port identification. Some people also seemed to think that the cuniform-style glyph in the below photo (far right) is a non-standard SCSI logo.
-- Beland ( talk) 12:17, 11 July 2008 (UTC)
Can anyone add logos for the single-ended, differential and LVD SCSI variants. Alecv ( talk) 11:33, 26 October 2009 (UTC)
I believe that this section has information mixed up; I don't have personal knowledge of SSA or SSA 40, but I do know that FC-AL is based on Gb (8Gb = 1GB).
This means that 1Gb, or 1000 Mb, would actually be 125 MB per second. Same for 2Gb, =250MB/s. 4Gb = 500MB/s. These are also theoretical throughputs, which noting that in the columns wouldn't hurt.
SAS has a 3Gb connection, not 3GB. 3Gb = 375MB/s. FC AL 8Gb & SAS 6Gb exist as well. Madrigaldeath ( talk) 22:21, 3 June 2011 (UTC)
This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
What is the sustained transfer rate for a 15000RPM Ultra320 SCSI drive w avg seek time of 3.3ms? is it still 320MB/s? for example an STA150 drive at 7500 RPM w avg seek time of 8.5 ms (16MB cache) has a sustained transfer rate of 64-35 MB/s & burst transfer rate of 150MB/s. -- Ario 12:34, 13 June 2007 ( 24.2.143.239 16:37, 13 June 2007 (UTC))
Fiber Channel is not an alternative spelling of Fibre Channel.
The concepts relevant only to SCSI Parallel Interface should be separated from the article on SCSI proper. Although SCSI-1 and SCSI-2 include SPI as a central part of the protocol, SCSI-3 has completely split the framework into separate layers. -- Cy jvb 20:20, 2 February 2006 (UTC)
Dis iz a good suggestion so I have split out the SPI content and created a new page called
Parallel SCSI.
Neilm
12:43, 7 February 2006 (UTC)
"SCSI is pronounced "scuzzy" when spoken aloud"... Isn't this a bit pleonastic? -- Edcolins 11:51, Oct 28, 2004 (UTC)
"while occasional attempts to promulgate the more flattering pronunciation "sexy" have never succeeded." Nowadays we're trying to get it to be pronounced "sucksy" ;) -- 148.84.19.92 15:25, 9 Mar 2005 (UTC)
The article says that PATAPI is SCSI over IDE. Isn't this a misnomer? As I recall, parallel ATA is not the only form of IDE, though PATAPI is, of course, over parallel ata.
good article, Mac users in particular grew up on SCSI and SCSI peripherals
How about some pics of the typical fat cables and giant terminators that people remember:
http://images.google.com/images?q=scsi&hl=en&lr=&sa=N&tab=wi
Also what about the SCSI logo ?
http://images.google.com/images?hl=en&lr=&q=scsi+logo&btnG=Search
I agree that this article needs some pictures. Anyone willing to take some? 203.208.80.13 00:51, 14 September 2005 (UTC)
hasn't Apple totally stopped using SCSI ???
Hasn't sun totally had sales of SCSI equipped systems plummet ?
Isnt sales of SCSI hardware now limitted to maintainance (including any strictly run enterprise that has SCSI as standard, so any new hardware must meet the old standard ...one would think that if they made the choice of standards now, they might chose SATA over SCSI .. ) and "main frames" situation, eg fibre channel for connecting 50 scsi devices to the 30 cpu supercomputer. —The preceding unsigned comment was added by 203.82.182.242 ( talk) 02:31, 17 January 2007 (UTC).
This article only seems to talk about devices...as far as I know, in the Linux kernel (for 2.6 at least), firewire IEEE1394 / USB storage devices / Ipod's, etc. they also use the SCSI protocol to communicate to the kernel. Any elaboration on this? -- Natalinasmpf 02:27, 19 Apr 2005 (UTC)
June 22, 2005:
The article should mention "packetized" SCSI that was introduced with Ultra-320. IBM preferred the term "information units" over "packets". I think this was around 2002 or early 2003.
Also, the "Ultra" designations were promoted by the SCSI Trade Association but not used in the ANSI standards. After SCSI-2, the physical interface standard was separated from the logical layers, and became SPI (for SCSI Parallel Interface) and went through generations SPI-1, SPI-2, SPI-3, SPI-4 and SPI-5. STA wanted marketing-oriented nomenclature that reflected the actual maximum data transfer rate of the bus. Note that the SPI acronym can easily cause confusion with other standards.
I don't think "All SCSI standards have been modular, defining various capabilities which manufacturers can include or not" is true of SCSI-1 or SCSI-2, which were monolithic specifications, unless "modular" means something different from what I take it to mean.
The description of the termination network is inside out and backwards. Passive termination uses 2 resisters to TermPwr and ground. Active termination uses 1 resistor to a regulated 3.3 volt source. Differential is 2 lines that are each terminated. In single ended, the other line is a ground. The active termination uses less power and therefore uses a smaller resistance that more closely matches the cable impedance. The tutorial that is already link to has it right < http://www.scsita.org/aboutscsi/SCSI_Termination_Tutorial.html>. It should also be mentioned that the term power fuses have mostly been replaced by a current limiting device. ~ Dan Oetting 136.177.111.33 00:32, 5 November 2005 (UTC)
Thanks. I got that wrong so I have now corrected it. neilm, 5 November 2005.
It's been a long time since I used SCSI. What is used now in servers? Isn't some form of IDE used now? -- Gbleem 16:13, 8 November 2005 (UTC)
In a read or write command block is the data transfer length in bytes or LBAs?
JimT
Always LBAs. See the SCSI Read Commands article for more info.
neilm
Note that Read/Write Long have a byte count in their CDBs. —Preceding unsigned comment added by 195.212.29.92 ( talk) 14:58, 5 January 2009 (UTC)
I miss the description of various SCSI connectors.
xerces8 -- 213.253.102.145 12:31, 16 January 2006 (UTC)
I have added a new page called SCSI connector
neilm 19 January 2006
2 Gbit isn't a clockspeed. In fact it's not a measure of speed at all. It's an amount of data. Clockspeed is measured in Hertz, and ONLY Hertz.
I think it should be made more clear what speeds the different SCSIs run at. Most transfer rates are defined as bits per second (bps) where as what is described here (Bps) which i have come to associate as Bytes per second. This does not, how ever translate over well when comparing transfer speeds.
So either the MB/s needs to be changed over to Mb/s or a subtle hint needs to be added to the text. Is this reasonable?
yet another Matt 14:30, 22 March 2006 (UTC)
What are the device size limits in SCSI ? This subject is always popular with ATA :-) Isn't there a limit at 2 TB (2^32 x 512 byte sectors) ?
- Actually, the new version of SBC supports 64x512 byte sectors, but sometimes the initiator or the OS doesn't support such big disk driver. —Preceding
unsigned comment added by
65.113.40.1 (
talk)
07:38, 10 September 2008 (UTC)
xerces8
--
213.253.102.145
11:00, 24 April 2006 (UTC)
There's nothing about "parallel port SCSI"... I gather it was used for a great many scanners and external disk drives, but beyond that, I don't know much about it. Also, I've seen ATAPI being described as partly based on SCSI, but I'm not sure whether to believe that. -- StuartBrady ( Talk) 14:34, 10 July 2006 (UTC)
The article states "You can attach both narrow and wide SCSI devices to the same parallel bus. To do this, you must put all the narrow SCSI devices at one end and all the wide SCSI devices at the other end, and terminate the high half of the bus in between (because the high half of the bus ends with the last wide SCSI device). "
According to Adaptec, a 68-to-50 pin adapter can be used to put a narrow device on a wide cable, and the high 9 part of the wide cable does not have to be terminated at that point. See Adaptec's KB answer ID 9, "Procedure for connecting both narrow and wide devices to a wide Adaptec SCSI card", in particular the description of the "Adaptec Internal Converter (ACK-68P-50P-IU)". Or are they wrong? Jeh 18:13, 3 August 2006 (UTC)
You can connect a narrow device in the middle of a wide bus.
You can connect a narrow cable to a wide bus, but you must terminate the high data lines at the point of connection between narrow and wide ...
Wide SCSI cards have which have a narrow cable connector usually have a way to terminate only the high data lines at the card. At the other end of the narrrow cable, you need to terminate (in the normal way for narrow), which can only terminate the low (narrow ) data lines ..
And at the other end of the wide cable, you need to terminate in the normal way for wide.
i noticed that on the table at the SSA row the Clock speed goes from Mhz to Mbit. to me that dont seem like it should be Mbit, seeing how it is a clock speed not a transfer rate.
longbow 17:58, 27 Sept 2006 (EST)
As its serial , which means one bit at a time, which means Mbit=MHz.
H for Mr Hertz. Its a name, so its capitalised.
This infobox really does not properly summarize the SCSI protocol suite, so I have removed it.
You could probably add this infobox to the SCSI_Parallel_Interface article, but you need to perform some fact checking first. -- Cy jvb 13:38, 11 October 2006 (UTC)
Consider me ignorant, but where and when is this possible? :: Colin Keigher ( Talk) 05:35, 21 December 2006 (UTC)
http://www.fibrechannel.org/OVERVIEW/topology.html Its very expensive, but it is technically a SCSI system that runs quite a long distance ... :)
In practical terms, its rare fibrechannel system, that is for mainframes, and outside of the scope of standard SCSI
FYI, I'm starting a major overhaul of this article. My goals include: make it easier to navigate; move the focus from SPI to the entire SCSI suite; add citations (to the actual T10 draft standards, when possible); add explanations or links for the tech terms; move individual SPI standard levels out of section headings and into a table, section, or article of their own. While I'm doing this, I may checkpoint with the organization somewhat less perfect than it could be. I may leave it for a day or four while I do things like work or sleep. But I will come back to it, and hopefuly quickly. I just wanted to let people I have a plan, and I'm not just chewing up the article for the heck of it. I'll try and note major progress here. Suggestions, comments, commendations, condemnations, etc., are welcome. — DragonHawk ( talk) 05:27, 17 January 2007 (UTC)
FYI, my own notes on this are at: User:DragonHawk/SCSI — DragonHawk ( talk) 23:47, 28 January 2007 (UTC)
availability of largest hard drives SATA drives: 800 gigabytes, reasonable price SCSI drives: 300 gigabytes, hideous price
Um, non-fibre scsi is dead. Perhaps mainframes will continue to use it, perhaps IBM will order or utilise SATA attached SCSI enclosures, putting SATA drives onto a SCSI bus..
Forgive me for being blunt, but you are just throwing wild speculation into the article (evidenced by your choice of words - probably, indicates, etc.). Your additions are based on a very narrow data point and obviously biased criteria. If you want to comment on the predominance of SATA-interfaced HDDs in the consumer market opposed to SPI-interfaced HDDs, then be my guest. Capacity and price would be obvious factors in the consumer market. You can even comment on the trend towards the cost-effective use of SATA HDDs in SPI/Fibre Channel RAID enclosures for the SMB. What you cannot do is unilaterally proclaim the death of a product (also insinuating the failure of a transport protocol) merely because you do not see a consumer mass-market appeal. There is plenty of information to cite to the contrary.
I'm going to withhold the unleashing of a revert war since in-depth discussion about SCSI HDDs is too SPI-specific anyway. Hopefully DragonHawk's overhaul will set the focus correctly on the protocol suite. Cy jvb 15:31, 18 January 2007 (UTC)
I agree. I am completely bemused by both the substance and the aggressive tone of this whole "controversy". I bought a small HP SCSI based server for £500 only a few months ago. Sure, SATA is more common now but there is no justification for pronouncing SCSI dead for hard drives, never mind for other peripheral types. While I don't like edit warring, I also don't like nonsense being left in the article either. I hope it will be corrected soon as part of the overhaul. -- DanielRigal 11:54, 19 January 2007 (UTC)
We just ordered a bunch of servers from Dell and ended up specifying 15k SAS drives because we need performance, not capacity. So, SCSI is most definitely not dead. Parallel SCSI is close, though. LTO-4 is probably going to be the last tape generation with parallel SCSI. Everybody *hates* SCSI-320, it's so marginal, and SAS is coming down in cost. Ralf-Peter 02:07, 12 March 2007 (UTC)
While I think that an IPA rendering would be lovely, I don't think we should have such a big ugly box on the article. What the heck is up with that anyway? I can hardly think of any article for which the most significant feature on first loading the page should be "Hey, we need IPA for this"; tons of things need or could use IPA, but unlike NPOV and Source Cite notices, I hardly see it as critical to paste a giant warning on. crappy template; where do we go to gripe about it? On the discuss page, a label like that would be ok as a sort of To-Do reminder. (Really, I think discuss pages should be supplemented by a bug tracking system so issues with pages could be neatly categorized, discussed, and resolved). Anyway, there should be a pronunciation section explaining the whole sassy/sexy/scuzzy thing; useful both to non-native/fluent english speakers and people interested in hilarious marketing debacles. But please talk about it here instead of edging towards revert battle. -- Akb4 09:43, 8 March 2007 (UTC)
Hi I have a technical question about scsi write which, if answered, should help improve the description of that command.
SCSI Write, all variants, specify a LBA into a LUN where the data is to be written. There is also a transfer length. presumably the data from a buffer is written to the start of a the specified LBA for the number of bytes in the transfer length. That in itself would be a useful explanation to have on the scsi write page.
however, what happens if the desire is to write, say, 1 byte at offset 10 inside of some LBA? The command does not seem to handle this sort of addressing. Certainly a user can modify a single byte of a file, say in C code.
Under the covers, does this sort of write involve a read to pull in the full 512 byte block, then the one byte is modified, followed by a write? I know this is a bit beyond the low level scsi protocol, which may just say you cant write a single byte, but isnt that what has to be done?
Kdohm 22:19, 29 March 2007 (UTC)
Yup - such is the nature of block addressing. See the SCSI Block Commands document (www.t10.org) for info on Write commands for block devices (disk). Note that for SBC, the transfer length is specified by the number of logical blocks, not bytes.
I think that you can use variable block mode to write a single byte with tape - at least it's valid as far as the command definition states (in this case, the transfer length is specified in bytes). Whether or not the device supports it is another question. Tape also supports relative read/writes depending on the current position of the tape. -- Cy jvb 01:54, 30 March 2007 (UTC)
I'm snipping this
pending a citation. Interesting if true, but we don't need a "some say" / "at some point" assertion in the article.
Along the same lines, long ago, in the heyday of Digital, when RT 128 in Massachusetts was a center of minicomputer development, SCSI was pronounced "sexy." I have no idea how or where ths could be verified, however. Cuvtixo 14:33, 21 August 2007 (UTC)
Vendors tried hard to promote the "sexy" pronunciation against the users seeming preference for "scuzzy". It didn't take. I remember meetings when we were switching from SASI controllers and drives to SCSI --- they'd say only "sexy" and we'd say only "scuzzy", though we were all talking about the same equipment: 5-20MB drives and controllers. ISC PB ( talk) 02:54, 19 November 2008 (UTC)
Does anyone have references as to when different commands were introduced like read(6), read(10), read(16). Which sets the absolute limit on how large discs that can be handled in practice (re ata 48bit mess). Electron9 04:49, 26 July 2007 (UTC)
One: BOTH of you are in violation of WP:3RR. Please allow a cooling off period.
Two: I personally find Tom94022's additional text: begs questions; answers no questions anyone was asking; is misleadingly specific (e.g. not every low level interface to which SCSI interfaced was ST506); incorrect factually (there is nothing as simple as a "bit serial" data stream in the ST506 interface); and poorly worded ("sectors (blocks) of bytes of data"). Apologies, Tom, but that's how I see it. Exactly what are you conveying here, and why does it need to be added to an article on SCSI, which long ago stopped being a bridge -- or an interface -- to another, older interface? Jeh ( talk) 07:26, 31 January 2008 (UTC)
The questionable sentence:
was added by by Bergert (Talk | contribs) at 06:09 on 30 January 2007 and has survived unedited for one year. You may think it is TMI but he did not and I do not, nor has anyone else for one year. Nor do I understand both of your continued and unexplained refusal to accept SASI as part of the history of SCSI - initially the major difference was the name. The only question on the table is what version we return to while we work out the dispute. So I am going back toward the original version but with some of what I believe to be obvious errors corrected. Since we are under WP:3RR policy, i believe it to be a violation if either of you then make any substantive deletions. Tom94022 ( talk) 20:14, 1 February 2008 (UTC)
Subsequent to the above posting IL2BA completely reverted three edits back to his singular version. I consider this to be a gross violation of the WP:3RR policy and have so reported it. It is particularly disappointing that he went as far as to suppress a correction (with reference) to the SASI announcement date, 1979 was not correct, but I guess accuracy doesn't matter in his zeal to own the page. Tom94022 ( talk) 23:01, 1 February 2008 (UTC)
Subsequent to the above posting IL2BA again completely reverted the three edits back to his singular version without any talk at all. Is he even bothering to read the edits? It is clear from a deleted reference that SASI was introduced in 1981 but he continues to revert to 1979 - is there some basis to his reversion other than he doesn't want it changed? It is clear from a deleted reference that SASI and SCSI-1 are the same thing (actually SASI is a compliant subset of SCSI-1)! Isn't this relevant and doesn't it rebut any contention that somehow SASI should be on a different page? It turns out because of my inexperience, my first posting at the Wikipedia:Administrators' noticeboard/3RR 3RR Administrators Noticeboard was not formatted properly and no action was taken, so I have resubmitted my request in what I hope is an appropriate form. Tom94022 ( talk) 07:10, 3 February 2008 (UTC)
((RFCsci | section=SASI as a part of SCSI History !! How much SASI history is relevant to SCSI !! time=19:00, 3 February 2008 (UTC)}}
It has been suggested that information about SASI in the SCSI history section is TMI (too much information) and on such a basis a number of edits have been disputed and continuously reverted. 216.103.87.80 ( talk) 19:00, 3 February 2008 (UTC)
Regarding the one remaining, second dispute, I am restating it below
I'm not wishing to throw gasoline on any fires, but I suspect that the less-than-exact use of the term 'analog' when referring to ST-506 bit-serial MFM signalling isn't entirely inaccurate, if you use it to mean non-digital. Where 'digital' would imply some sort of fixed clock or framing type of system such as RS-232 has. ST-506 didn't, and was merely a faster form of the common floppy interface at the time, where the bit serial stream was wobbly and about as raw as could be had. I don't think there was much more on the drive than the usual head amplifier, one that used differential signalling for the hard disks. The required clock/data separator (for reading) was the hard part! I don't know if there is a term suitable for use between analog (obvious) and what is commonly thought of as a digital interface. ISC PB ( talk) 03:11, 19 November 2008 (UTC)
I struck out the malformed RFC at the beginning of this section. Since there have been no substantive comments proposing the deletion of the SASI material from the article I am going to delete the dispute tag from the History section. Tom94022 ( talk) 18:10, 9 February 2009 (UTC)
SCSI is a peripheral interface: up to 8 or 16 devices can be attached to a single bus.
It appears that SATA and SAS now own the hard drive market, and parallel SCSI is nearly obsolete.
Looking around on big-name drive manufacturer websites, I cannot find any information about current parallel SCSI drives bigger than 300 gigabytes, and that drive size has been available for a couple years now. Meanwhile there are many SAS drives over 300 gigs:
Are any new parallel SCSI drives still being manufactured? DMahalko ( talk) 08:20, 26 October 2009 (UTC)
In the server marketplace the fastest drives are the most expensive, and pushed as being the "enterprise class" models. However, if you have a 300 gb 15000 RPM drive, and a 600 gb 7200 RPM drive, both with the same number of platters, is the 15000 RPM really faster? Or is the performance going to be about equal?
Perpendicular recording allows a higher sector density per cylinder, so a 7200 RPM drive with twice the sectors per track of the 15000 RPM drive should apparently perform equally.
It would appear that what Seagate calls their "enterprise class nearline storage" 2 TB 7200 RPM SAS, will probably have performance at least equal to, or exceeding the abilities of their 600 gb 15000 RPM drives. Since the 2 TB drive has about 3 times the cylinder data density of the 600 gig drive, and it appears that it may perform as well as a 21,600 RPM enterprise class drive.
DMahalko ( talk) 08:28, 26 October 2009 (UTC)
I'm looking at the Parallel SCSI table in the article and am a bit confused over a couple of the maximum length entries. Both "Fast SCSI" and "Fast-Wide SCSI" have a maximum single-ended length of "1.5–3 m". I believe this should simply be "3 m".
I recognize that both "Ultra SCSI" and "Ultra Wide SCSI" have max lengths that vary between 1.5 meters and 3 meters based on the number of devices connected to the bus, but have been unable to find any such reference for Fast SCSI.
Unfortunately I don't have access to the actual SCSI specifications. Can anyone verify whether or not the article is correct?
ChadCloman ( talk) 05:34, 19 March 2010 (UTC)
"U320" redirects to the SCSI page. However, there is no mention of "U320" in the article, so the meaning of the term and the purpose of the redirect both remain obscure. 207.188.235.142 ( talk) 19:03, 3 June 2011 (UTC)
It would be useful to have the standard diamond logo in this article, to help in port identification. Some people also seemed to think that the cuniform-style glyph in the below photo (far right) is a non-standard SCSI logo.
-- Beland ( talk) 12:17, 11 July 2008 (UTC)
Can anyone add logos for the single-ended, differential and LVD SCSI variants. Alecv ( talk) 11:33, 26 October 2009 (UTC)
I believe that this section has information mixed up; I don't have personal knowledge of SSA or SSA 40, but I do know that FC-AL is based on Gb (8Gb = 1GB).
This means that 1Gb, or 1000 Mb, would actually be 125 MB per second. Same for 2Gb, =250MB/s. 4Gb = 500MB/s. These are also theoretical throughputs, which noting that in the columns wouldn't hurt.
SAS has a 3Gb connection, not 3GB. 3Gb = 375MB/s. FC AL 8Gb & SAS 6Gb exist as well. Madrigaldeath ( talk) 22:21, 3 June 2011 (UTC)