Re: [Xen-users] Linux software RAID1 (Dom0 or domU)?

[Javier Guerra <javier@xxxxxxxxxxx>]

On Thursday 01 February 2007, Petersson, Mats wrote:
> I agree that hardware raid is the leanest option (cpu-wise, maybe not
> for the bank).

most 'hardware raid' cards are far worse, both in performance and cpu-usage, 
than the linux md module.

also, in RAID 1 all writes are done twice, so it has to go twice through dom0.  
i guess it's a far worse thing than doing it all in dom0.  the md module is 
_very_ lean and optimised.

for RAID 5 it might be even worse to do in domU, because to get good 
performance it's very important to get whole stripes in cache.  to do in dom0 
you'd need more RAM there than the minimum, but in several domU you'd have to 
get the same 'extra' several times.

and, of course, if you do in Dom0, you can split it with LVM, and all domU's 
benefit.

-- 
Javier

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