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Fixed capacity SCSI flash drives/DOMs?

Franklinstein

Well-known member
Some people may be familiar with ATA disk-on-module drives, which are basically anywhere from about 1-32GB of fixed storage in a module that plugs directly into an ATA header. There are no flash cards, no USB connectors, no configuration software, no nothing: plug it in and presto! You have a disk drive ready to go. Does anybody know of a DOM-type drive for SCSI? I did a little searching and while I did find a handful of SCSI flash drives, most seemed to either be variations of SCSI2SD or they were a little vague with "call for pricing/availability" on some of the websites, which means either it's at least as expensive as a SCSI2SD solution and/or they're not available without ordering half a million of them.

While I do appreciate the versatility and available features of SCSI2SD and other projects, in most cases I don't need it. At all. Also, >$100 plus the cost of the flash card is a little steep if all I want is a boot drive for an SE, a system that would be more than happy with under 1GB of storage. And it's not as if I'd be shuttling the drive around between machines: once it goes into a PB 550c or a Color Classic, it's staying there forever, so there's no need for the ability to swap cards and fiddle with virtual disks or anything.

So yeah: do any exist, and if not, is there interest in having something made? I figure four flavors (512MB, 1GB, 2GB, 4GB) would be adequate and cover pretty much the whole spread of machines that would benefit from such a drive (if you have a PCI-based Mac most chances are you'd probably prefer using a SATA or ATA card for mass storage, and if you need more than 4GB a SCSI2SD may be more cost effective anyway). Having a single 2.5" form factor would mean it would slot into either a PB directly or into a desktop with an adapter. It would be fully plug-and-play: install it and the system sees the full capacity of the disk straight away, no pre-configuration required. Ideally prices would range from about $30-80 or thereabouts depending on capacity and also possibly upon what type of flash is used (I'd prefer the long-life NAND stuff over cheap SD card flash, especially if a *nix or VM were used).
 

lisa2

Well-known member
AFAIK, a SCSI DOM does not exist. ATA DOM's are only cheap because hundreds of thousands of them were made. Have a look into the BlueSCSI project: https://scsi.blue/
You can buy these pre-made for $25 plus the price of a SD card.
 

Cory5412

Daring Pioneer of the Future
Staff member
Prior to their entry into the vintage computing hobby with SCSI2SD, SCSI disk replacers will have been niche products that cost lots of money because they were aimed at sustaining the lives of "money counter" type minicomputer and mainframe machines whose platforms mostly ended on the eve of the switchover to SATA. Imagine a disk that casually costs three thousand dollars and you buy a hundred of them to put into a computer that originally cost you a few hundred thousand dollars, which keeps track of hundred of millions or billions of dollars.

SCSI SSDs do exist, but in the secondary market, they are either:
- You live in California or another Major Tech Hub and picked one out of the trash
- Thousands of dollars because I Know What I Got and/or someone's still trying to support a moneycounter or a similar legacy system.


One general note: it seems like on the SCSI2SDs at the very least, they benefit from buying a fairly fast SD card. This is extremely true in the V6 and is probably "still true, but less" in the v5.

Also, one other note: You do not have to limit yourself. 040s in particular should support basically any volume size so on, say, your PB550 there's no reason not to set up a SCSI2SD v5 with a 32-gig card in it as, like, a 30-gig volume. Absolute worst you can partition it in software after the fact.

(well, okay, so, SCSI manager 4.3 on the '040 macs and system 7.6.1 through 9.2.2 supports a max volume size of 2TB, so once we get SD and MicroSD cards in that size range it may be worth being careful.)

I'm sure you know this but just so it's written down: although IME and from what I've seen here the SD card SCSI replacers are way more reliable than the original hard disks, it's worth noting that they're not completely infallible so it'll still be worth running backups using whatever methodology. If your systems are on a network you should be able to just retrospect them or copy your whole drive over periodically, depending on what your needs are.

Also, >$100 plus the cost of the flash card is a little steep if all I want is a boot drive for an SE, a system that would be more than happy with under 1GB of storage.

SCSI2SD should meet this need well. I have a few v5s that I've configured, put in machines, and then stopped thinking about.

In the US, SCSI2SD v5 variants seem to be going for around $70, which is more than I remember but less than you'll pay for what you're describing.

I don't know what local-to-German pricing is, however.

You can buy these pre-made for $25

Which one?

I browsed around and could not find any pre-assembled for under $50. The $25-30 prices I found are all for kits. One one Euro reseller I looked at, the assembled BlueSCSI was 63 Euro.

In addition, it appears stock numbers do vary between the main project page and each vendor, so when you're ready to buy, you may need to hunt for available inventory.

There's a couple other notices saying the micro controller the BlueSCSI uses is becoming more difficult to find and "prices reflect this" -- tough to say if that's the same reason the SCSI2SD v5 appears to have risen in price a bit.
 

lisa2

Well-known member
OK, I stand corrected. The $25 price is for a kit and not "pre-made" as I had stated.
With the current global supply chain / chip shortage issues the prices of all this stuff will continue to rise even from the "non-greedy" sellers.
 

Franklinstein

Well-known member
So Hagiwara seems to offer something in the "industrial SSD" area that would be ideal but they're in that "contact for quote" group and are likely to be pretty expensive. Also the ones I saw were 3.5" and I'd also like a 2.5" option. They may have one but I was having trouble searching their site earlier. Maybe I should contact them and ask how much they want for 1000 of the 2GB models and if it's reasonable I'll keep 100 and sell 900 of them on eBay for a markup.

Anyway one of the benefits to the Hagiwara drive is that they're using proper SSD-rated NAND flash with (presumably) proper flash controllers, not running a minimal SD card controller. While most applications running classic Mac OS without VM won't likely notice problems, anything with VM and/or a *nix (such as A/UX) will likely exceed the number of write cycles the SD card can sustain fairly quickly, and it's not likely the flash controller software is robust enough to compensate for this. They may not even do wear leveling in the first place, which will significantly shorten the lifespan of the SD card (unlike CF, SD requires the host controller to do all the management tasks). Granted I don't have a ton of info on how either SCSI2SD or BlueSCSI projects perform flash management, but it's not likely to be comprehensive (at least, not compared to a proper SSD). Basic searches didn't turn up too much technical info but then I didn't go much further than a page or two of search results.

Also minimum file sizes get ridiculous once you're over about 10GB in HFS. It's something like 160kB even here. Most machines targeted for SCSI2SD won't properly support HFS+ so if you put an HFS partition on a 32GB flash drive you'd be looking at something like 500kB as the minimum file size. Plus, I have no need nor want for that much space on a 68k box. I'm sure someone out there would like to put every piece of 68k software available onto one, or have it chopped up into 10 different partitions with different software configurations on each, but I don't need that. I need basic drives from 512MB~4GB. I'm sure there are other people out there would would also like this sort of thing without having to assemble or 3D-print stuff, with an up-front total cost (in addition to supplying your own flash card, SCSI2SD and BlueSCSI generally requires purchasing/creating additional stuff before the final product is ready to go into a machine, specifically housings/mounting brackets and connectors).
 

Cory5412

Daring Pioneer of the Future
Staff member
I think an important point here is that nearly 20 years worth of different Macs can boot off of SCSI devices. Even some machines that were sold next to each other (like the Performa 600 and Quadra 700) have significantly different disk and volume handling capabilities. It even changes on some machines based on what OS is installed (e.g. on a Q700: 7.1 2gb limit, 7.5 4gb limit, 7.6.1 2TB limit; or on a P'Mac G4: 2TB under OS 9 and 16TB under 10.4.)

Here's the limits: https://68kmla.org/bb/index.php?threads/volume-size-limits-under-hfs-and-hfs.3872/

I think most people need to understand what problem they're solving before trying to solve it and I think there's no reasonable "one size fits all" or even "one size fits most" option here.

How each person with an old Mac with low volume limits handles that fact will really depend on their own preferences and needs. I've seen plenty of people use just the first couple gigs on a 32-gig SD card. I have an Apple IIgs with 256 megs worth of a 32-gig CF card formatted.
 

Scott Squires

Well-known member
A lot of people have trouble getting their disk images set up on their SD cards. They want something that is simple and plug-and-play. But I don't know that this solves that problem. I have the impression that a lot of people need to be able to access the drive from their modern computer. To do the initial install, to load software, or to retrieve data. If that ability isn't there, then the complexity of managing disk images is traded for complexity of bootstrapping vintage hardware.

I probably wouldn't use it if it didn't feature a USB mass storage mode. I could imagine some people would like it though.
 
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