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Re: [Xen-users] best practices in using shared storage forXENVirtualMach

To: Jeff Sturm <jeff.sturm@xxxxxxxxxx>
Subject: Re: [Xen-users] best practices in using shared storage forXENVirtualMachines and auto-failover?
From: Freddie Cash <fjwcash@xxxxxxxxx>
Date: Thu, 14 Oct 2010 09:09:18 -0700
Cc: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
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On Thu, Oct 14, 2010 at 8:59 AM, Jeff Sturm <jeff.sturm@xxxxxxxxxx> wrote:
>> -----Original Message-----
>> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
>> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Freddie Cash
>> Sent: Thursday, October 14, 2010 11:38 AM
>> To: xen-users
>> Subject: Re: [Xen-users] best practices in using shared storage 
>> forXENVirtualMachines
>> and auto-failover?
>> > You don't need a clustered filesystem.  You don't need a shared
>> > filesystem at all.  Just partition your shared block storage (with a
>> > clustered logical volume manager if needed) and use a logical volume
>> > for each domU image.
>> Would you run the iSCSI initiator in the host and attach the block device to 
>> the guest?
>> Or would you run the iSCSI initiator in the guest?
> I like to do the former.  That makes the guest easier--you don't have to 
> figure out things like modifying initrd to do boot-from-SAN.
>> How does the migration from one host machine to another work with iSCSI?
> No different than migration with any other shared storage.  Just make sure 
> each dom0 has a working initiator, and is logged into the appropriate 
> targets.  If your SAN has ACLs, you'll need to allow access from every 
> possible dom0.

So how does the migration work?  This is the part that is still
tripping me up.  :)

You have HostA configured with the iSCSI initiator, with VM1 using the
block device for storage, running all happily.

Then you tell VM1 to migrate to HostB.

Does HostB already have the iSCSI initiator running?  Does it get
started when the migration starts?  What happens to the initiator on

I understand how it works with an NFS share and a disk image file.
It's the whole "exported block device on the network" bit that's
messing me up.

Freddie Cash

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