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

Jake Smith jsmith at argotec.com
Thu Mar 13 15:36:32 CDT 2014


Thanks Francis. wish that was it that but it's write back.

 

We even bought a new 6/I and replaced the 5/i (now it matches the other
2950/6i system) and there was no change in performance.

Everything except the CPU and memory chips are identical between them
except one hits 140/MBs and the other only 20.

 

Jake

From: francis picabia [mailto:fpicabia at gmail.com] 
Sent: Thursday, March 13, 2014 3:26 PM
To: Jake Smith; linux-poweredge at dell.com
Subject: Re: [Linux-PowerEdge] PE 2950 PERC 5/i slow

 

 

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
<mailto: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 


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