[Linux-PowerEdge] PE 2950 PERC 5/i slow

francis picabia fpicabia at gmail.com
Thu Mar 13 14:25:56 CDT 2014


In case this helps...

We went through troubles with 2950's and Perc 5.  They all had a battery
which worked
but was below a threshold.

Here is how to test:

omreport storage vdisk

Look for "Write Policy".  If that line shows "Write Through", you are
getting crappy
performance because it won't use the memory cache on the controller.  The
disks
need to wait for another clock cycle before they can write again.  You must
replace
batteries on these before they completely fail.  I think it was something
like below
30% rating the policy switches from Write Back (fast) to Write Through
(slow).
There is also a message like this from Open Manage in the logs:

Jan 18 07:25:39 myserv Server Administrator: Storage Service EventID: 2335
Controller event log: BBU disabled; changing WB virtual disks to WT:
Controller 0 (PERC 5/i Integrated)

It is nasty because the performance degradation does not come with any
alarms
or errors, just a quiet drop in performance.





On Mon, Feb 24, 2014 at 1:13 PM, Jake Smith <jsmith at argotec.com> wrote:

> Hi All,
>
>
>
> I have two PE 2900's with identical 4x500GB Seagate SATA 7200 RPM drives
> in a RAID 10 on each.  Both running Ubuntu 12.04 Server x64 with the latest
> updates applied.
>
>
>
> Write test:
>
> dd if=/dev/zero of=/tmp/test count=5 bs=512M oflag=direct
>
>
>
> The PE with the PERC 5/i is getting about 20MB/s write speed regardless of
> write back/write through.
>
> The PE with the PERC 6/i is getting about 140MB/s with write through, 180
> with write back on the controller.
>
>
>
> Both have batteries and I've swapped them to rule out a failing (not
> reported) battery
>
> Swapped controller port 0 and 1 on the PERC 5 card.
>
> Pulled one drive at time and restested, pulled 1 and 2, pulled 1 and 3 -
> all no change.
>
> Tests all yield 18-20MB/s.
>
>
>
> Ran dstat - nothing using the drives
>
> Checked for any updated firmware - using the latest 5.2.2.0072.
>
> Driver version is 00.00.06.12-rc1
>
>
>
> Any ideas on what else to try or test?  I'm at a loss since I would expect
> something in the 70MB/s range from one drive alone and I'm not even in the
> ballpark.
>
>
>
> Jake
>
> _______________________________________________
> Linux-PowerEdge mailing list
> Linux-PowerEdge at dell.com
> https://lists.us.dell.com/mailman/listinfo/linux-poweredge
>
>
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