Friday, 1 July 2011

Citrix XenServer Notes

Started cutting my teeth on this plaform recently and I am impressed with
it so far. I have had a few roadblocks along the way - one of which
involves the fact that the default install for XenServer is to format the
Local Storage has LVM rather than EXT3. The advantages are speed and you
can do cool things like live migration, etc. Disadvantages include the
tree or chain style of block allocation that makes it impossible to delete
VDIs once created, or to resize them. Once you delete a VDI you seem to
lose the allocated disk space forever as they become part of the "base
copy" mess and if you remove any of the "base copy" VDIs you can corrupt
the SR entirely and will result in having to re-create the SR from
scratch. So LVM is good if you plan it out properly and have more than one
SR in your system so you can move things around and free up space that way

Some commentary:

Another way is to replace the default LVM SR with a file-based EXT3 SR. The
advantages are VDIs are easily resizable and you can copy them around
easily as they are just files. Once you delete them - they are gone,
freeing up any space used. Another thing is they are sparsely allocated so
they won't actually use any physical disk space until they contain data.
Another advantage is you can use the Head-Start restore feature provided
with StorageCraft ShadowProtect among other things.

Follow these instructions to create the EXT3 SR:

XenServer 5.6 Documentation:

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