Monthly Archives: October 2012

Xenserver LVM over iSCSI

Trying to reclaim space from that VM you deleted several months ago?

This is a known issue with Xenserver and iSCSI when snapshots are used.

The short answer is that if you allow your SR to fill up too much, the automatic coalesce leaf operations performed by XS will not be able to be performed as a certain amount of space is required for this function to reclaim space.

The basic rule is that there must be Double the VM size of free space on the SR available for the coalesce function to work.

So if you delete a 100GB VM, you MUST have at least 200GB of free available space on the SR.

minimal centos

Remove those ugly useless packages from your CentOS 6 Server!

gluster path stale usage path

Using parted to create partitions

hp sim xenserver agents..

ls -ld /

does it return

drwx—— 24 root root 4096 Feb 5 16:41 /

then execute this!

chmod 755 /

Start all VMs on HOST boot

place the following in /etc/rc.local

sleep 30
xe vm-start tags=autostart –multiple

mark all VMs with autostart tag and they’ll be started!

IPoIB tuning

startup script

in cron
@reboot /etc/path_to_script


echo “connected > /sys/class/net/ib0/mode”
echo “connected > /sys/class/net/ib0/mode”

ibconfig ib0 mtu 65520
ibconfig ib1 mtu 65520

#make sure sdp is loaded… just in case!
/sbin/modprobe ib_sdp

#TCP Tuning for IPOIB
/sbin/sysctl -w net.ipv4.tcp_timestamps=0
/sbin/sysctl -w net.ipv4.tcp_sack=0
/sbin/sysctl -w net.core.netdev_max_backlog=250000
/sbin/sysctl -w net.core.rmem_max=16777216
/sbin/sysctl -w net.core.wmem_max=16777216
/sbin/sysctl -w net.core.rmem_default=16777216
/sbin/sysctl -w net.core.wmem_default=16777216
/sbin/sysctl -w net.core.optmem_max=16777216
/sbin/sysctl -w net.ipv4.tcp_mem=”16777216 16777216 16777216″
/sbin/sysctl -w net.ipv4.tcp_rmem=”4096 87380 16777216″
/sbin/sysctl -w net.ipv4.tcp_wmem=”4096 65536 16777216″