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RE: [Xen-users] XCP Storage

  • To: <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "Brett Westover" <bwestover@xxxxxxxxxxx>
  • Date: Wed, 26 Oct 2011 13:13:29 -0700
  • Delivery-date: Wed, 26 Oct 2011 13:14:48 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcyUCaqKAb/TAONrRY6dAAkSIBIDGgADuB6g
  • Thread-topic: [Xen-users] XCP Storage

>Also, it seems I am reading that you can enable live migration on an XCP pool 
>without an external storage device at all, using >local storage in each host. 
>Is that right?
>How does that work?

>My understand of shared storage is that one copy of the VM exists in a place 
>accessible to the two hosts, so to do live migration >the VM storage doesn't 
>actually move.

>Can someone point me to some documentation that explains how XenServer and XCP 
>handle storage? It seems to be quite different than >VMware.


>Brett Westover

>I don't think it's that different. If you want to do migration your storage 
>needs to be remote. Currently XCP seems to support two >types of remote 
>storage that can support migration - NFS and iSCSI software target. 

>Grant McWilliams

Well, then that clears that up... unless someone comes along and disagrees :)

I thought I heard somewhere you could use DRBD storage on two servers, and use 
that for your VMs. Since the volumes exist on both servers, you could do 
migration. But I think that was with a customized server running Xen (not XCP).

So, since you previously said that with XenServer you've measured significantly 
better performance (especially on writes) with iSCSI over NFS, then it seems 
what Iâm looking for is an iSCSI SAN (which is what I have now). I'm using 
DataCore SanMelody, and we like it just fine, but to add a second server and 
mirroring is VERY expensive (5 figures just for the licensing).

Since we're looking at converting as much of this to open source products as 
possible, are we looking for OpenFiler? FreeNas? 
I think you mentioned building a Centos server w/ storage, and then presenting 
that with built in iSCSI support.

Looking for advantages/disadvantages.... We are not against buying an 
enterprise product like NexentaStor if necessary to get the features we need, 
we just can't justify anything like what we'd pay now for those (things like 
Active/Active mirroring as a primary example), from DataCore.

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