Re: [Xen-users] Fwd: Xen - large virtual machines

[John Madden <jmadden@xxxxxxxxxxx>]

>       * We are required to be able to bring up VMs on one machine on
>         another within a reasonable period of time (this is defined as
>         days, not hours) and to keep the backup copy reasonably in
>         sync (again, days not hours). Can anyone comment on the
>         suitability of rsync to copy such massive block devices? We
>         would use version 3, which I know has improved performance for
>         this sort of move, but is it going to literally take forever
>         to checksum 48TB? If anyone is able to give example of rsync
>         performance (same switch or crossover - whichever we conclude
>         is fastest) over gigabit Ethernet, that would be a bonus. We
>         expect there to be significant spare resources available to
>         domU at night for checksumming if required.

Use block replication software to replicate block devices.  gnbd, for
example, will work fine.

> The VMs are expected to be quite IO-heavy, hence the requirement for
> local storage (not iSCSI) and para virtualization.

Then take another look at your storage setup -- depending on what you
mean by "IO-heavy," those boxes may not perform all that well.  Are you
talking thousands of small i/o's, which would be bad, or hundreds of
large i/o's, which would probably be fine?

John



-- 
John Madden
Sr. UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@xxxxxxxxxxx


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