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Bug#498228: marked as done (linux-image-2.6.24-etchnhalf: Horrible RAID iowait problem)

Your message dated Mon, 15 Feb 2010 18:33:05 +0100
with message-id <20100215173305.GM9624@baikonur.stro.at>
and subject line Re: linux-image-2.6.24-etchnhalf: Horrible RAID iowait problem
has caused the Debian Bug report #498228,
regarding linux-image-2.6.24-etchnhalf: Horrible RAID iowait problem
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
498228: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=498228
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Package: linux-image-2.6.24-etchnhalf
Severity: normal


We upgraded to this kernel on a Dell PowerEdge server with a Dell PERC 6
RAID controller.  This uses the megaraid_sas module.

Under even small amounts of load the RAID then generated so much iowait
the system was unusable.  This was easily repeatable and very seriously
nasty.  We experienced no problems under the previous 2.6.18-6 kernel.

You can see an example from top here:

Tasks: 127 total,   1 running, 126 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni, 74.3%id, 25.7%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   8307748k total,  3476056k used,  4831692k free,    10332k buffers
Swap:  2000084k total,        0k used,  2000084k free,   793932k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
    1 root      20   0  1940  632  540 S    0  0.0   0:01.48 init
    2 root      15  -5     0    0    0 S    0  0.0   0:00.00 kthreadd
    3 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/0
    4 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/0
    5 root      RT  -5     0    0    0 S    0  0.0   0:00.00 watchdog/0
    6 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/1
    7 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/1
    8 root      RT  -5     0    0    0 S    0  0.0   0:00.00 watchdog/1

iowait got as high as 70% on a basically idle system.

Here's some output from iostat:

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00    69.65  0.00  0.00     0.00     0.00     0.00    78.34    0.00   0.00  99.50

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           6.94    0.00    0.25   34.58    0.00   58.23

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     0.00  0.00  0.00     0.00     0.00     0.00   159.00    0.00   0.00 100.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.64    0.00    0.19   48.96    0.00   49.21

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     0.00  0.00  0.00     0.00     0.00     0.00   158.56    0.00   0.00  99.50

Again, whilst basically idle the utilisation is showing as 99.5%.  Utilisation at times went well over 100%, to perhaps 120%.

We've gone back to the previous kernel and now experience no problems.

Cheers,

Doug.

-- System Information:
Debian Release: 4.0
  APT prefers proposed-updates
  APT policy: (500, 'proposed-updates'), (500, 'stable')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.18-6-686-bigmem
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)

--- End Message ---
--- Begin Message --- 
closing as outdated and no longer supported linux image.
assumed fixed since. also no follow up since.

thanks for the report.

--- End Message ---
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