Checking for swappers on XenServer

This article will outline the steps I take to check for swappers on my XenServer and XenClassic stepups.

XenServer

• Log into the huddle the host in question is located in
• Log into the host the slice/instances is located on
• Run iostat to check for any swappers on this host:

iostat -xkd 1

• If swappers are found, cat the device of the slice to get its minor number:

cat /sys/block/tdk/dev  # returns something like: 1234:20

• Get the UUID for this slice

tap-ctl list | grep minor=20

• Check if this slice is a "swap" partition (make sure it is _not_ a root partition!):

xe vdi-list uuid=xxxx-xxxx-xxxx-xxxx

• Check to make sure no other tasks are currently being perform on this host

xe task-list

• Now force a reboot

xe vm-reboot --force name-label=slice01234

• Check that the slice has actually rebooted:

xe vm-list name-label=slice01234 params=start-time

• Verify that the output from the last command is within the current timestamp

date

That's it! You can successfully killed a swapper and brought the slice back up to a normal load.

XenClassic

This is how you do the above on a XenClassic setup.

• Log into the huddle the host in question is located in
• Log into the host the slice/instances is located on
• Run iostat to check for any swappers on this host:

iostat -xkd 1

• If swappers are found, list the device mapper for this slice:

ls -l /dev/mapper/ | grep ' 20 '

• Now "destroy" that slice (we are not permanently destroying this device, that's just the terminology):

xm destroy slice01234

• Finally, re-create this slice (this takes information from a configuration flatfile found under /etc/xen/slice01234):

xm create slice01234

That's it! You can successfully killed a swapper and brought the slice back up to a normal load.