Re: [Xen-users] Xen and iSCSI - options and questions

[jpranevich@xxxxxxxxxxx]

----- "John Madden" <jmadden@xxxxxxxxxxx> wrote:

> Why not just side-step all of this and do your iSCSI initiating in
> dom0,
> then LVM the LUN and boot the domU off of a phy: allocation?  I've
> seen
> several posts lately regarding the complexities of iSCSI, booting
> domU's, etc., and I'm wondering why no one is just treated like
> normal
> SAN or SCSI LUNs.

Because the iSCSI hardware (Equallogics) I'm using has a maximum of 512 
concurrent iSCSI connections per volume group. I have a Xen cluster of 40 
servers and since each would need persistent connections to the iSCSI for each 
possible host that could live on it (since I want migrations to be free; I've 
written some software for this using the Xen-API that does simple load 
balancing), that means I could only have 12 total virtual machines. And that 
doesn't work well at all. :)

If the hardware didn't have a low limit, I would be doing exactly as you 
indicate since it's a much cleaner solution overall. But I have a lot of $$$ 
invested in the gear now.

(Other options include using LVM and having each domU server using a different 
slice of the same LVM, but I've read elsewhere that it isn't cluster-safe yet 
for cases where you need to add or remove volumes from the group, etc. I don't 
know the specifics since I read that weeks ago.)

Joe

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