[rescue] SCSI Replacements (was: IDE SSDs? I never knew...)

[Patrik Schindler]

Hello,

(not a reply to Jan-Benedict in particular but more a general idea.)

Here are my $.02:

Almost all of the currently known solutions for the replacement of real SCSI drives seem more or less botched to me, in addition to probably being inferior in performance due to limitations in CPU processing power, polling instead of interrupts, media being slow on the eventual image store, etc. The biggest advantage of those is: They are readily available and seem to work.

I was considering an older release of SCST on Linux for a while, to build an external storage-server (HP Microservers come to mind) connected via parallel SCSI cable to the machine in question.

https://scst.sourceforge.net/

I feel this might provide adequate performance for typical servers or workstations from back-in-the-day. I'm especially thinking about AS/400's, which have intricacies of their own: Hammering out many small I/Os per second, requiring 520 or 522 Bytes per sector, some guaranteed "vital product data" responses, and at least two additional vendor specific SCSI commands being required (SKIP_READ, SKIP_WRITE).

Unfortunately, the SCST project dropped parallel SCSI support quite a while ago, but using an older version with an older kernel is a viable way around this. As far as I've understood, target mode for parallel SCSI HBAs is limited to LSI chipsets.

Someone on the SCST mailing list pointed out that FreeBSD has similar support built-in. It involves recompiling the kernel, though. Advantages are: Still works in current releases, supports more than just LSI chipsets in target mode.

I have finished a basic install of FreeBSD some weeks ago on a HP Microserver N54L with an LSI card I had spare. Next steps would be to find out how to configure things to make them work like I want and test with a stock 512 Bytes/sector system. Have enough old Macs spare for that purpose. :-)  Unfortunately, there's always more to do left at the end of a day.

If anyone is interested on picking out the thread and help: You're most welcome!


Am 29.06.2024 um 21:13 schrieb Jan-Benedict Glaw via rescue <rescue at sunhelp.org>:

> I especially love the PiSCSI thingie! As I am on the way setting up
> automated testing for operating systems on old hardware (Linux and
> NetBSD installations), it's helpful to be able to "change" the
> emulated CD installation media over network. So I can build some OS
> install media, deploy it to PiSCSI, power the target system, install
> everthing (by using `expect`) and test the resulting system, all
> without rotating rust.
> 
> MfG, JBG

:wq! PoC