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

[Doug Ledford <dledford@redhat.com>]

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

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  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
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