[rescue] IDE SSDs? I never knew...

[Dave McGuire]

   That's exactly what I would think, if there were ever any implication 
about a SCSI mass storage device being a hard disk drive, but there 
hasn't.  It was always (by far) the most common implementation, but it 
was never a requirement that anything be rotating, and there were 
other-than-HDD SCSI mass storage devices since the beginning of SCSI.

               -Dave

On 6/30/24 06:49, Mike Spooner via rescue wrote:
> I feel that HDD Emulator is fair, rather than SCSI Emulator.
> 
> - Mike
> 
> 
> On 28 June 2024 15:20:30 BST, Dave McGuire via rescue 
> <rescue at sunhelp.org> wrote:
> 
>     On 6/28/24 10:04, Jonathan Chapman via rescue wrote:
> 
>             Another is that they don't talk directly to the hardware;
>             they speak
>             some other disk interface protocol, such as SATA, out the
>             other side.
> 
> 
>         Moreover, they are often talking to something FAT32 formatted,
>         and storing the SCSI targets as files. They can also be CD-ROMs,
>         Ethernet adapters, etc.
> 
>         Compare to an ACARD SCSI to IDE [to SATA] bridge, where you talk
>         to the disk 1:1 w.r.t. blocks. Those are closer to a host
>         interface bridge, IMO. More like a HVD <-> LVD bridge than
>         whatever you want to call the modern iterations.
> 
>         I think calling something like the BlueSCSI, ZuluSCSI, SCSI2SD,
>         etc. an "emulator" is probably not wrong.
> 
> 
>     Most if not all SCSI hard drives have a processor on them,
>     frequently an i80186 or an Hitachi SuperH. What gets stored on the
>     platters is completely opaque, and in many cases contains error
>     control information, block remapping data, etc etc, i.e. a lot more
>     than end-user data. There may be some form of filesystem involved,
>     who knows? But even that term has a loose definition.
> 
>     The interface to the platters is something very different from SCSI.
>     Somewhere there's a dividing line between "analog" and "digital",
>     but the line where it becomes "SCSI" is a good bit further in the
>     same direction. Nearly all SCSI hard drives store data in an RLL
>     format. The SCSI layer is unaware of it.
> 
>     My point is, there's always stuff going on under the hood. The
>     difference here is that with a ZuluSCSI or similar, we can see
>     what's under the hood. So it's an SD card, something that we
>     recognize as being also available for other applications. Does that
>     make the whole assemblage an "emulator"? No. It's not emulating a
>     SCSI mass storage device, it IS a SCSI mass storage device. Not an
>     emulation, but an implementation.
> 
>     -Dave
> 
> 
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-- 
Dave McGuire, AK4HZ
New Kensington, PA