1U VAX, was: Re: Computer stores

John H. Reinhardt johnhreinhardt at thereinhardts.org
Tue Aug 25 16:07:57 CDT 2020

On 8/25/2020 3:00 PM, David Brownlee via cctalk wrote:
> On Tue, 25 Aug 2020 at 19:46, John Klos via cctalk
> <cctalk at classiccmp.org> wrote:
>>> I was going to comment that the only way I could see a 1U VAX was if
>>> someone rack mounted a 4000/VLC.  Is that the stock VLC power supply?
>>> My cluster doesn?t even have that much space.
>>> What do you use to go from SATA to SCSI (SCSI-1 even)?
>> It's a standard 1U power supply with a custom adapter. You can see it
>> better here:
>> https://twitter.com/AnachronistJohn/status/1294725819038752768
>> I use a SATA to IDE adapter, then an IDE to UW-SCSI adapter, then an
>> UW-SCSI cable and terminator, then finally a 68 to 50 pin adapter.
>> The previous drive was a Samsung SSD, but I think that constant, non-stop
>> swap use wore it out. This was the smallest new spinning rust drive I
>> could find.
>> SCSI2SD would work for a while, but, again, swap usage would wear out an
>> SD card in no time, I'm sure.
> Wow, I'm surprised the VLC could generate enough traffic to wear out
> an SSD - compared to a modern box running heavy compiles and suchlike.
> Very cool box :)
> Thinking about SCSI devices for my collection of older boxes - I
> wonder if rascsi set to use the pi's RAM rather than an SD card to
> provide a swap device would work out.
> Actually, could be interesting to run a modern *nix box with the right
> type of scsi adapter in target mode and have it "export" devices and
> or ramdrives to older boxes...
> David
Make sure you use a higher quality SD card.  Something labeled "High Endurance" or "Industrial".  They have internal wear leveling firmware to spread the writes/erases out over the memory array and help keep it from getting any hot spots that wear out quickly.  It won't last forever but it will help it last longer.

Examples: High Endurance: <https://www.amazon.com/dp/B07B9KTLJZ>

Industrial: <https://www.amazon.com/gp/product/B07CV344WJ>

It may seem wasteful, but if planning on long life for an SD card that is the O/S drive then get something big and only use a portion of it so that the wear leveling can work with more.  So if you want a 16GB disk, then get a 32GB or even 64GB SD card and use SCSI2SD's internal partitioning to only use 1/2 or 1/4 of the full drive.

That's my theory anyway.  I'll let you know in a year or three if it worked. I have SCSI2SD in two AlphaServer DS10's, a MicroVAX 3100 and a PDP-11.  I also use the same theory in a couple Raspberry Pi's.  The Pi's use log2ram for the /var/log files to help also. They don't actually swap much.

John H. Reinhardt

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