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

[Peter Petrakis]

That's never how it works. multipath has no kernel module loading ability. Would
make a nice feature though. I admit that discovering "which dh
is the necessary one" is a bit arcane and not well documented anywhere.

The best practice here is to load the necessary device handler into your initrd so
it's attached at the same time the SD devices are initially discovered. You still
need to have this module loaded to provision additional luns at runtime and
not have their performance plummet.

Also, I discovered a typo in the multipath documentation.

 https://bugs.launchpad.net/serverguide/+bug/1057071

Had that worked to begin with, you would have never encountered this
issue in the first place. 

Closing this issue as "Invalid" as it's not a bug. Thanks for the
report.

** Changed in: multipath-tools (Ubuntu)
       Status: Incomplete => Invalid

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https://bugs.launchpad.net/bugs/1057054

Title:
  poor performance after upgrade to Precise

Status in “multipath-tools” package in Ubuntu:
  Invalid

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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