Completely Agree. The multi-initiator point is the one I try to hammer
home. It's what the
current algorithm completely misses.
Even though I said its complex - it's really not that difficult. The
pain is just figuring out
what to group and what the rates should be.
-- james s
Matthew Wilcox wrote:
On Thu, Apr 16, 2009 at 10:13:42AM -0400, James Smart wrote:
However, for arrays, with multiple luns, the queue depth is usually a
target-level resource,
so the midlayer/block-layer's implementation falls on its face fairly
quickly. I brought this
If the problem were as simple as the resource being target-level instead
of LUN-level, it would be fairly easy to fix (we could do accounting
per-target instead of per-LUN). The problem, AIUI, is multi-initiator
where you can't know whether resources are in use or not.
up 2 yrs ago at storage summit. What needs to happen is the creation of
queue ramp-down
and ramp-up policies that can be selected on a per-lun basis, and have
these implemented
in the midlayer (why should the LLDD ever look at scsi command
results). What will make
this difficult is the ramp-up policies, as it can be very target
device-specific or configuration/load
centric.
While not disagreeing that it's complex, I don't think putting it in the
driver makes it less complex. I completely agree that LLDDs should not
be snooping scsi commands or scsi command results. It should all be in
the midlayer so we all share the same bugs ;-)
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