Exploring XenServer 5.6 Free Edition

Citrix XenServer was starting to provide a Free edition from last year. The features of the free edition are comparable or more than what VMware ESXi provide. I decided to give it a try for its Latest XenServer v5.6 to see how well it will fit into my  requirement.

1. The 1st thing I noticed is the broader hardware supported by XenServer. I install XenServer on an ordinary PC with Core i7 860 & ASUS P775D-E DELUX MB. It can detect the on board NIC (rt8196) without problem. Unlike VMware ESXI which only officially support Intel Pro1000 and Broadcom tg3 NICs, I believe XenServer can support most of the NICs which are supported by  linux natively.

2. Then 2nd thing I would like to do is to examine the possibility of using Linux software-raid on it as I cannot do this under VMware ESXi which support only hardware RAID controller. I found that this is quite easy to do which there’re a no. of docs in the net. Some of them even teach you how to make XenServer’s system files stored on linux software raid. Currently I only want to store VM images on a software RAID. A good document is available there : Software RAID on XenServer.

The steps in short :

a. create fd partition : /dev/sdb1, /dev/sdc1
b. mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 \
/dev/sdb1 /dev/sdc1
c. mdadm --detail --scan > /etc/mdadm.conf
d. xe sr-create content-type=user type=lvm shared=false \
device-config:device=/dev/md1 name-label=SoftwareRAID-1
e. Enter the following command to set your SR as the default SR on the system :
 xe pool-param-set default-SR=YOUR NEW SR UUID uuid=(press tab because you have a single pool)
f. Enter the following command to set your SR as the default location for suspended VM images:
xe pool-param-set suspend-image-SR= YOUR NEW SR UUID uuid=(press tab because you have a single pool)

[Note: MD is broken in XenServer 5.6. A workaround is available there : In short,  edit /etc/rc.d/rc.sysinit, remove the line ” [ -x /sbin/nash ] && echo “raidautorun /dev/md0″ | nash –quiet” and create /etc/mdadm.conf to start MD]

3. The 3rd thing to test is the migration of VMware Guest vm to Xen. This part is proofed the most difficult due to the different hardware emulation of the two platforms. Although Xen provide a software called XenConverter to do the job, this doesn’t make the job easier as it is just a format converter. The main problem is how to to retrofit the original VMware Guest hardware into the most basic one which Xen also support as well. This is a really daunting task and it seems those platform’s V2V converter doesn’t help much.