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

[Peter Petrakis]

Then we might have a distro bug here, which is weird as I've done hundreds of
SAN installs with lucid and have had to manage the scsi_dh modules everytime.

So on your lucid system,  /etc/initramfs-tools/modules should be empty
except for the commented out examples.

The next thing to check is the initram disks themselves, assuming there's no
directives in the previous config file, the presence of the scsi_dh kos in
the initrd would indicate that they were be globbed in by another
initramfs helper.

Actually...

root at nashira:~# zcat /boot/initrd.img-3.2.0-26-generic | cpio -it | grep scsi_dh 
lib/modules/3.2.0-26-generic/kernel/drivers/scsi/device_handler/scsi_dh_hp_sw.ko
lib/modules/3.2.0-26-generic/kernel/drivers/scsi/device_handler/scsi_dh_alua.ko
lib/modules/3.2.0-26-generic/kernel/drivers/scsi/device_handler/scsi_dh_rdac.ko
lib/modules/3.2.0-26-generic/kernel/drivers/scsi/device_handler/scsi_dh_emc.ko
81384 blocks
root at nashira:~# zcat /boot/initrd.img-2.6.32-41-generic | cpio -it | grep scsi_dh
lib/modules/2.6.32-41-generic/kernel/drivers/scsi/device_handler/scsi_dh_hp_sw.ko
lib/modules/2.6.32-41-generic/kernel/drivers/scsi/device_handler/scsi_dh_alua.ko
lib/modules/2.6.32-41-generic/kernel/drivers/scsi/device_handler/scsi_dh_rdac.ko
lib/modules/2.6.32-41-generic/kernel/drivers/scsi/device_handler/scsi_dh_emc.ko
64508 blocks

OK, I'm surprised :)

In my 2.6.32 initrd I find:
root at nashira:~/2.6.32# cat conf/modules 
scsi_dh_alua

which I suppose prompts my device handler to be installed. Which is driven
by 'modules' and 'modules.d' in /usr/share/initramfs-tools. So the modules
apparently have always been there, thanks to this hook script.

/usr/share/initramfs-tools/hook-functions


        scsi)
                copy_modules_dir kernel/drivers/scsi
                for x in mptfc mptsas mptscsih mptspi zfcp; do
                        manual_add_modules "${x}"
                done
        ;;

Which is how the scsi_dh_* kos got on the initramfs, but that doesn't
explain how it was loaded. That directive had to come from somewhere,
so it's either already in your /usr/share/initramfs-tools/modules|modules.d
or it's in your /etc/initramfs-tools/modules.d|modules and you missed it.
*something* has to be prompting it's inclusion.

What's the output of, as root?
grep -Rl scsi_dh /etc /usr/share/initramfs-tools/

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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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