View source for Checking for swappers on XenServer

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

==''XenServer''==
* Log into the huddle the host in question is located in
* Log into the host the slice/instances is located on
* Run <code>iostat</code> 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 performed on this host (except for "pending: reboot"-like statuses):
 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 have 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 <code>iostat</code> 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 <code>/etc/xen/slice01234</code>):
 xm create slice01234

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

We can accomplish the above with a single script (well, a series of CLI calls) like so:
 (echo "device name tps MB_read/s MB_write/s MB_total/s";\
 (ls -l /dev/mapper/; iostat -m 1 2) |\
 awk 'BEGIN {section=0} {\
   if($3=="root") devices[$6]=$9;\
   if($1=="Device:") section++;\
   else if(section==2 && $0) {\
     dev=$1; tps=$2; read=$3; write=$4;\
     if(substr(dev,1,2)=="dm") {split(dev,parts,"-"); name=devices[parts[2]]} \
     if(!name) name="unknown";\
     print dev" "name" "tps" "read" "write" "read+write}}' |\
 sort -k3n) | column -t

And, if the above command(s) return a slice id, then execute:
 xm destroy slice01234 && xm create slice01234 && xm console slice01234

===XenClassic slice configuration file===
Below is an example of what a slice configuration flatfile (which is, by default, located at <code>/etc/xen/slice01234</code>) would look like:
 name="slice01234"
 memory=512
 vcpus=4
 kernel="/etc/xen/seeds/01/vmlinuz-2.6.35.4-generic"
 ramdisk="/etc/xen/seeds/01/initrd.img-2.6.35.4-generic"
 vif=['bridge=eth0, ip=xxx.xxx.xxx.xxx, mac=4f:d0:c4:10:ab:0c','bridge=eth1, ip=10.x.x.x, mac=4f:e0:29:9f:c3:fe']
 disk=[ 'phy:slices/slice01234_root,sda1,w', 'phy:slices/slice01234_swap,sda2,w' ]
 root="/dev/sda1 ro"
 cpu_weight=512
 extra="xencons=tty console=tty1 clocksource=acpi_pm "

where,

:memory = how much RAM should be allocated for the slice
:vcpus = number of virtual CPU's that should appear within the customer's environment (default: 4)
:kernel = which kernel seed the slice should use
:ramdisk = the initrd that corresponds to the kernel being used by the slice
:vif = sets IP's and MAC addresses for the various network interfaces on the slice
:disk = the storage volumes that the slice will use
:root = the storage volume that should be used as the root filesystem
:cpu_weight = helps to calculate the slice's share of the CPU (equal to RAM)
:extra_ips = if the slice has additional IP's, they will be listed here
:extra = additional Xen settings

[[Category:XenServer]]