LVM, iSCSI and Xen

[Louis Guillaume <louis%zabrico.com@localhost>]

Hi,

I'm designing a system where I will have iSCSI targets on one machine 
exported to a number of virtual machines (in PV mode) on another machine.

(All this is still depending on my getting iscsi-initiator to work 
properly, but I expect that will happen shortly. So I haven't tried any 
of this yet.)

I have 2 choices for this setup and I wonder which will yield the better 
performance:

 (1) mount the iSCSI targets on DOM0 and set them up as disks in
     the DOMUs' configurations.

 (2) mount the iSCSI targets directly in DOMU

Are there pros/cons to either of these? I guess it would come down to 
the performance of the xennet interfaces vs. xbd disk-devices.

For storage management I plan to do it all on the iSCSI-target machine. 
So each target will be dedicated to a certain DOMU.

I did consider using LVM in DOM0 to manage storage. The storage machine 
would serve up chunks of disk and then the DOM0 would figure out who 
gets which piece. I would consider this again if the xbd devices proved 
to have better performance. But controlling things on the storage side 
seems to be more flexible, especially when it comes to deciding what 
disks, controllers etc. are exported for what reason.

Any thoughts on these topics would be most useful to me,

Louis