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

To: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, "Marduk" <xen@xxxxxxxxxxxxxxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Linux software RAID1 (Dom0 or domU)?
From: "Liang Yang" <multisyncfe991@xxxxxxxxxxx>
Date: Thu, 1 Feb 2007 09:37:22 -0700
Delivery-date: Thu, 01 Feb 2007 08:37:27 -0800
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Mats,

The problem when you use guest domain to create MD-RAID array is that the array will only be visible to that guest domain. If we create array in domain0, we can make it visible to all guest domains.

I think this is also the benefit to use domain0 to manage MD-RAID array.

Regards,

Liang

----- Original Message ----- From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
To: "Marduk" <xen@xxxxxxxxxxxxxxxxxxxxxx>; <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Thursday, February 01, 2007 8:38 AM
Subject: RE: [Xen-users] Linux software RAID1 (Dom0 or domU)?




-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Marduk
Sent: 01 February 2007 15:29
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Linux software RAID1 (Dom0 or domU)?

Just wondering if anyone has had any experience with this.

I'm thinking about setting up a 2-drive RAID1 set using Linux software
RAID.  The question is, as far as performance is concerned, which is
better:

      * Let dom0 handle the RAID and pass the volume to domU or
      * Pass both drives to domU and let it handle the RAID.

I would have thought that the performance penalty for software raid
would be about equal - however, there is a difference between loading
Dom0 and DomU if you have more than one guest-domain - Dom0 will be used
by all domains, so any extra load on Dom0 will affect all domains,
whilst extra load in DomU only affects that DomU. Particulary, latency
for each domain will be higher if Dom0 is handling the raid.

That's my thoughts on the subject, and be aware that I've never run
software raid on any system ever!

--
Mats

thanks in advance,
-m


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