[dm-devel] [PATCH 4/7] scsi_dh: add EMC Clariion device handler
Chandra Seetharaman
sekharan at us.ibm.com
Tue Apr 22 23:45:53 UTC 2008
On Tue, 2008-04-22 at 16:47 -0500, Mike Christie wrote:
<snip>
> > wait
> > ******************************************************
> > Simple Run:
> >
> > with patchset: 2.6.25-mm1:
> > real 3m30.122s real 3m29.746s
> > user 0m4.069s user 0m4.099s
> > sys 0m14.876s sys 0m14.535s
> > -----------------------------------------------
>
> Is this just a boot up test or a test just running IO but no
> failback/failover?
Test running IO but no failover/failback.
>
> >
> > Failover Run:
> >
> > with patchset: 2.6.25-mm1:
> > real 5m18.875s real 5m31.741s
> > user 0m4.069s user 0m3.883s
> > sys 0m14.838s sys 0m13.822s
>
> Ehh, I have no idea if this is good or bad. Does it mean it is talking
> 13 more seconds to complete?
It is taking 13 more seconds without the serialization :) (i.e the old
code).
>
> Have you seen the type of thread on dm-devel or the iscsi list where
> people are concerned with getting the time the failure is detected to
> the time IO is running on a new path down from something like 10 to 5
I totally agree with you that shaving a second here and a second there
has lot of value to the customers.
>
> seconds. One time the iscsi driver did not implement time2wait correctly
> and by fixing it we shaved only 2 seconds off and users were very happy
> with the extra 2 seconds. We added the nop timer stuff so we could get
> faster failovers. We have the fast io fail tmo so we can speed up the
> process even more. Shaving off a second here or there is really nitpicky
> and if I were you I would give me the middle finger :) It just seems
But, I wouldn't :)
>
> like people expect better performance from this type of error.
>
> If my comment is too nitpicky then I am fine with ignoring this for now.
> We just have to fix the emc short/long tress pass code then. I added
> another EMC guy to the thread so he can ping the other EMC devs to get
> going (I had sent them questions on how to handle it and have not got a
> response).
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