Does SCSI still exist?

[Zak33]

While looking at the HEXUS render farm .. .it occurred to me...

Where has SCSI gone?

Is it dead?

I had loads of SCS kit loooong ago.. more than the mobo and CPU were ever worth at the time. HDD and CD roms

[jim]

While looking at the HEXUS render farm .. .it occurred to me...

Where has SCSI gone?

Is it dead?

I had loads of SCS kit loooong ago.. more than the mobo and CPU were ever worth at the time. HDD and CD roms

Serial Attached SCSI (SAS) is still very much alive and kicking.

Don't know much about it, mind.

EDIT: I'm splurging on a new (to me) server to all of this has been floating around my mind for the past few days.

[scaryjim]

Wikipedia tells me that there are all sorts of SCSI interfaces, including variants over fibre channel and USB!

But assuming you actually mean parallel SCSI - which was at one time the de facto standard for server hard drives - apparently it struggled with inherent problems using high speed parallel buses. Apparently it's easier to drive serial buses to higher clock speeds, so they dropped into serial-attached variants - the current version of SAS allows for 12Gbps (twice the speed of SATA 3), and the next generation (due this year, apparently) will go up to 22.5Gbps (while also changing the encoding scheme, so the actual data rate will still double - like they did with PCIe 3). That'll give SAS 4.0 a bandwidth of 2.4GB/s, vs 320MB/s for the last generation of parallel SCSI....

[Kumagoro]

I don't know about other people's data centres but the one I am at has basically stopped using SAS drives and just uses tiered storage of SSDs and SATA to save money as that is more than quick enough.

[scaryjim]

I don't know about other people's data centres ....

It's not actually my team, but I know that another team in my unit is currently speccing up a shared storage platform which is built on a multi-tier basis with SSDs (possibly NVMe? Not 100% sure!) as the top tier, backed with slower rust drives. I might have to go and be nosy and see if they're going with SAS or not!

I'm pretty sure the last servers I specced were RAID 1 SAS, but that was around 6 years ago and they were lowish load web servers - I just went for whatever looked easiest on the configurator

[peterb]

Yes, Ultrium tape drives up to Ultrium 4 used parallel scsi and Adaptec still make parallel SCSI cards. Cables are hard to find though.

Parallel SCSI came in several variants, the last was 320 differential voltage - the cables were individual twisted pairs in a ribbon with both cores active.

SCSI itself is more than a physical interface - it is actually a communication protocol (like ATA, for example) and as PATA moved to serial, so did SCSI. So it is medium independent which is why it can be found in fibre channel applications and also as SAS. You may find it in SAN applications, or in data centres, but others may know about that.

One interesting application is iSCSI, which is basically SCSI over IP used for (very) remote storage drives.

[Saracen]

While looking at the HEXUS render farm .. .it occurred to me...

Where has SCSI gone?

I think most of it is in my parts cupboard, or various PCs.

[DanceswithUnix]

If you still have a CD-rom, DVD drive or similar in your computer, you might be interested to know that ATAPI is basically SCSI over IDE.

SAS is still in use in some data centres where racks of drives are connected via fibre channel to redundant raid controllers into redundant servers. Private cloud systems will probably cause a move to distributed filesystems on a pool of servers using NVMe flash storage, but I think we are a few years off that happening yet.

SCSI has traditionally been kept alive by its ability to do lots of requests in flight to lots of drives on a single interface. NVMe can do basically 4 billion outstanding requests (sort of, certainly more than enough) and if drives become distributed across compute servers again rather than centralised onto a traditional NAS or SAN then SAS will probably wither leaving just iSCSI (SCSI over ethernet) and SCSI over USB as fringe uses.

SCSI has had a long and distinguished run, but NVMe is better and storage wants to be lower latency in most cases these days than SCSI can manage.

[Dashers]

Just as Parallel ATA was succeeded by Serial ATA, SCSI went Serial Attached SCSI, or Fibre Channel :/

[Saracen]

....
SCSI has had a long and distinguished run, but NVMe is better and storage wants to be lower latency in most cases these days than SCSI can manage.

Agreed, but at least in my case, it's primarily about legacy hardware that I already have, which works well (or at least, well-enough for my needs) and which would cost a fortune to replace.

For instance, an A3 flatbed scanner, and 3 film scanners (Nikon, Canon and Minolta respecticely).

Also, while I don't dispute the latency point, I still have an old server running 6x SCSI hard drives in RAID 5, with spares including several identical hard drives, 2 spare SCSI controllers, and even two spare replacement hot-swap drive cages. The demands I put on this are nominal, and again, replacing it would be expensive.

I wonder how much legacy SCSI kit, like this, is out there?

To be clear, if I were buying now, SCSI is not the route I'd go. But it works, works well and does what I need of it. And, I've already got it.

[DanceswithUnix]

I wonder how much legacy SCSI kit, like this, is out there?

I have a QIC tape drive, a 5GB DAT drive, a bunch of hard disks and a CD rom which I basically use as a terminator
None of it has been plugged in for years, just sat in a cupboard along with the NCR810 PCI SCSI controller which was the last one I had.

Yeah it was awesome in its day to the point to the point it is still usable if you can stand the noise of all those old hard drives.

SCSI hasn't really been in home kit for decades, and in business use will be discarded after 5 years of use when drives go out of warranty and support contract. But even if big storage systems move to distributed VSAN storage, you will still get VMs using iSCSI so the protocol will be with us for years.

Edit: Oh, I still have a 50 way crimp tool somewhere if anyone had cable problems

[Saracen]

I doubt SCSI was ever common in home use - too expensive.

As for "business use" .... that depends on the business. Don't forget, not sll businesses are big, with big budgets, and managers spendingcsomeone else's money. For 'corporates', I'd agree with your analysis. But I've come across countless small businesses, including mine where the criteria are very different from 'out of warranty or support contract'. In fact, I've come across some kit I reckon was bought used, from Noah when he decommissioned the Ark.

The way I look at it is if it'll cost me thousands to replace, and the existing kit is still working perfectly, then that's thousands out of MY bank account into someone else's for .... what, exactly?

A lot, I'd argue, deoends on what it's used for. If it's mission-critical, then the risk and potential cost goes up, and yeah, a pre-emptive replacenent or upgrade might be in order. But otherwise, it can be money down the drain. This is why many of my (airgapped) legacy machines are still running XP. And will, until they die, or much more likely, I retire fully.

[peterb]

The first Apple Mac(intosh) in 1985(ish) had a SCSI hard drive and a SCSI external connector for expansion. This was before IDE was developed and the ST 506 interface with a separate drive controller card was the norm. SCSI was a major advance. It was the development of IDE that drove the price down below that of the equivalent SCSI drive.

[DanceswithUnix]

I doubt SCSI was ever common in home use - too expensive.

As for "business use" .... that depends on the business. Don't forget, not sll businesses are big, with big budgets, and managers spendingcsomeone else's money. For 'corporates', I'd agree with your analysis. But I've come across countless small businesses, including mine where the criteria are very different from 'out of warranty or support contract'. In fact, I've come across some kit I reckon was bought used, from Noah when he decommissioned the Ark.

The way I look at it is if it'll cost me thousands to replace, and the existing kit is still working perfectly, then that's thousands out of MY bank account into someone else's for .... what, exactly?

A lot, I'd argue, deoends on what it's used for. If it's mission-critical, then the risk and potential cost goes up, and yeah, a pre-emptive replacenent or upgrade might be in order. But otherwise, it can be money down the drain. This is why many of my (airgapped) legacy machines are still running XP. And will, until they die, or much more likely, I retire fully.

In the 386/486 days when IDE was young SCSI was all over the place. OK we were fairly high end, but I and all my friends had SCSI drives and Adaptec controllers. The IDE and MFM/RLL drives of the time were slow polled affairs whereas SCSI was busmastering DMA even on an ISA bus. If you only ran Windows 3.1 then polled was fine, but for those of us running Linux IDE hammered the multi tasking performance. When the PCI bus came out we switched to NCR controllers as they were cheaper and faster, but we stuck with SCSI for some time. Small businesses generally had a Novell Netware server using a 486 and an Adaptec controller with SCSI drives.

Heck, if you had an Atari ST with a hard disk you had a SCSI drive (and I did ).

My PC switched to IDE when the drives could do decent DMA on a VLB controller. Lack of command queueing was unfortunate, but the performance became close enough.

I didn't say that *all* businesses use SAS drives.
Of the businesses buying storage, some will be buying for high availability and/or buying by the petabyte. In both cases you will be using fibre channel and SAS enclosures though you might have SATA drives with SAS adaptors plugged in as the actual storage. SAS can easily do that.

If you have a petabyte of SAS drives or a 5x9's requirement, then you probably really care about that data. The MTBF for drives is only valid for the warranty period, so when your 5 years is up you are expected to rip that storage out and replace it, and that will be budgeted for. In fact, you will probably see hot swap metrics across your hundreds of drives which tell you they are getting unreliable. Again, if you are cheap you won't be in that position, it is pretty specific to people with that need. I have yet to come across a private individual with a million pounds worth of storage setup though, so I only see SCSI/SAS drives in old obsolete servers bought off ebay in private hands.

These days if you are spending a million on storage, you expect flash and it probably won't be SAS or SATA based on that scale. Things move on.

[Saracen]

Been there, done that. I started my (8088/8086) PC days with 20MB MFM drives, progressing to SCSI via ESDI, which was a mahooooosive 338MB, and a not-so-cool £1500. That, for the youngsters, was the bare drive, not the PC. This was, IIRC, 1983 or 84. Then I went to a brand new Wyse 386, with a 330MB SCSI, 150MB tape drive and a £10k price tag. And I could have bought a house for less.

My experience, DWU, of those days was that it was relatively advanced small-er businesses that had computers at all, abd most of those that did didn't have the staff or expertise for Unix/Linux. Heck, I made a good living supporting them.

That's the background to SCSI I was talking about - small businesses with between one and maybe half a dozen PCs and, by and large, SCSI was toomexpendive, too niche and unnecessary for the uses PCs were put.

On the other hand, if you had specialist needs .... SCSI was it. I did. Firstly, driving CD burners, with AV-rated Mictopolis drives, when you daren't use IDE, etc, becsuse if they T-CAL'd in the middle of a burn, you turned a £15 blank CD into a coaster. Then, a bit later, the scanners that were inputs for a variety of output devices, including plotters, cutters, etc.

But for those running office admin, WP, accounts, etc, SCSI was overkill.

[DanceswithUnix]

Been there, done that. I started my (8088/8086) PC days with 20MB MFM drives, progressing to SCSI via ESDI, which was a mahooooosive 338MB, and a not-so-cool £1500. That, for the youngsters, was the bare drive, not the PC. This was, IIRC, 1983 or 84. Then I went to a brand new Wyse 386, with a 330MB SCSI, 150MB tape drive and a £10k price tag. And I could have bought a house for less.

You are targetting a few more years further back than I am, hard disks were rare until the very late 80's regardless of interface. But 330MB, jeeze I think that was the capacity of the top loading disk packs on the VAX 11/780 I used to use which were used to run an entire engineering division of a large international company. As a programmer in 1986 I was using a 10MB MFM hard drive on a PC which was enough for DOS, GEM (Windows was unusable, the cool kids ran GEM) and my development environment and it was a bit of a squeeze. An upgrade to 20MB gave me plenty of room, I can't imagine what you were storing on a drive that size in those days!

My first drive personally owned by me was a 30MB SCSI drive for my Atari ST which was 1987. I can't remember the exact price, but I was a student at that point so it can't have been stellar, a few hundred I think including the external hard disk case & psu. From that point and for about the next 5 to 7 years buying SCSI vs RLL/IDE was like the choice you have now between a cheap spinning disk and a flash drive. There is a clear performance advantage to the flash drive, and a clear price penalty, but the price penalty is within the reach of many so plenty of people take the hit.

My first PC was when I heard about Linux so about 1992. It was a 386/40 and I used an Adaptec 1542A ISA bus SCSI controller, I was not long out of University and still steeped in student dept so couldn't afford a 486, but I could stretch to SCSI. SCSI wasn't *that* expensive if just used as a better IDE interface.

Edit: When my housemate bought a 486 machine he used an Asus 486PCI/I-SP3G motherboard which had a SCSI controller built in, an enthusiast grade motherboard. That was probably peak SCSI, before IDE started becoming usable enough with interrupt driven DMA interface as well as cheap.