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SubjectRe: devfs
Leonard N. Zubkoff writes:
> From: Bob Tracy <rct@gherkin.sa.wlk.com>
> Date: Wed, 14 Jan 1998 07:29:40 -0600 (CST)
>
> Time to lay it to rest, but here's a way for folks to live with 'd'
> and 's'. Think 'd == device, s == subdevice' and assign whatever
> meaning is consistent for a particular type of device. In the
> System III/V way of naming things, 'd' was never intended to represent
> 'disk'. The original meaning of 's' is a bit more obscure, and 'slice'
> was at least as common an interpretation as 'subdevice' as I remember
> it. Regardless, 'stripe' or 'strip' wasn't one of the valid meanings.
> In my mind at least, there's a natural correlation between a
> subdevice and a partition, and 's' isn't as limited as 'p' if/when
> you want to apply the naming scheme to a device that doesn't have
> partitions.
>
> An example: for SCSI devices, '(d)evice == LUN'.
>
> One more example: ESDI disks. On the old 3B2 computers with ESDI
> disks, a SCSI target ID (t1-t7, t0 was reserved for the host adapter)
> corresponded to a SCSI <--> ESDI controller (Everex) that could
> support up to four spindles (d0-d3). Simple math implies you could
> hang up to 28 spindles off a single SCSI host adapter if you were
> crazy enough to put up with the I/O bottleneck.
>
> The ESDI example in particular is why I would prefer 'd' to 'u', but
> I can live with 'u' if that's the consensus.
>
> The device/subdevice explanation makes a great deal of sense, and
> would allow extending the naming consistently to non-SCSI devices
> where the use of logical unit and slice isn't appropriate. If it's
> not yet too late, I think this is a good argument for using "d" and
> "s".

I guess I could live with that. It would actually bring things more
into line with Solaris 2 (except that we have a bus identifier as
well).
However, since you raise this again, Leonard, what about the issue of
slices within a partition? It appears that Solaris two places multiple
slices inside a standard MS-DOS-style partition. What would you
suggest to handle that? How about:
/dev/sd/c0b0t0d0p1s6 :-)

Regards,

Richard....

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