Re: [PATCH + RFC] Beginning of some updates to scsi mid layer

Doug Ledford
2002-06-28T07:37:04Z

On Thu, Jun 27, 2002 at 10:41:31PM -0700, Jeremy Higdon wrote:
> Is there any accounting for the following condition:
>
> An array with multiple logical units can accept 256 commands (for
> argument purposes) from all initiators for all luns. Therefore,
> the number of commands that you can queue to sdX is dependent
> on how many commands queued by this initiator to other sds, as well
> as how many commands other initiators have issued to this sd and
> others.

That's (currently) on a per driver basis. My driver would account for
this situation just fine. Others might not. That is one of the things I
plan to change in the mid layer very soon now.

> This may not be an issue so much with parallel SCSI RAIDs, but it does
> come up with Fibrechannel.
>
> It is theoretically possible to get QUEUE_FULL when the host has no other
> commands in progress on a logical unit. Would the host driver then believe
> that it could issue 0 or 1 command only, or is there some lower limit?
>
> jeremy

--
Doug Ledford <dledford@redhat.com> 919-754-3700 x44233
Red Hat, Inc.
1801 Varsity Dr.
Raleigh, NC 27606