[Bug 1057054] Re: poor performance after upgrade to Precise

Chris Weiss cweiss at gmail.com
Wed Sep 26 23:21:58 UTC 2012

after the upgrade and initial reboot, I change the config file and
verified multipath -ll  was as I expected, then rebooted and did the pv
test.  I did nothing else between my first posting and the reply
verifying lsmod, so yes, it was loaded on reboot.

I have both controllers in the md3000i, and each has 2 ports.  a LUN can
be on either controller, and active/active on that one controller, with
the other controller as standby.  I also have luns on it used by esxi,
and the RR paths appear to be the same.

I did not check which driver got loaded on lucid, and the dell docs are
really kinda all over the place so I was trying to ignore them.  rdac
did seem to be what was happening based on how multipath -ll showed
things, and I did see roughly equal traffic on 2 nics.  In my first
attempt with Precise I did initially see the ping-ponging you mention,
before I understood how to apply rdac configs.  With Lucid I put the
rdac config in right from the start and did not see that behavior.

is it possible the old mpath_prio_rdac callout was loading the driver
early in the process?  I was not aware of scsi_dh_rdac's existence until
this thread, so I have no explanation of how it's getting loaded when
you think it shouldn't be.

it's nice to see the config codified, I'll have to experiment with that
some.  thanks for that info.

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  poor performance after upgrade to Precise

Status in “multipath-tools” package in Ubuntu:

Bug description:
  I had a Lucid x64 server working with a Dell MD3000i with 4 paths and
  worked as expected.  I added the "prio rdac" line to the conf file,
  then upgraded to Precise, and removed the old mpath_rdac line and
  reboot one more time, just to be sure.  I did this based on a section
  in https://help.ubuntu.com/12.04/serverguide/serverguide.pdf

  as a "sanity check" test, I'm doing 'pv < /dev/mapper/dellsas1 >
  /dev/null' (friendly names enabled).  On Lucid i'd get about 100MB/s
  After upgrading to Precise I get an almost solid 768kB/s.  If I
  instead use the 4 underlying /dev/sd* devices, 2 give errors as
  expected, and 2 run at about 100MB/s as expected so iscsi seems to be
  working correctly and multipath not.

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