Typically,
you would have a third box which acts as a SAN. It's probably possible to use
a local DRBD device between the two hosts, but I don't like that idea. =)
From:
xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Marc A.
Müller
Sent: Wednesday, September 24, 2008 12:41 AM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Best way to redundant images?
Sorry
for asking again for an easy way for redundant xen images. After reading some
threads and numerous howtos i'm a bit confused.
I
have two xen hosts, each of them has one disk and should be the host for
several domU's. Live migration should be supported. If one host fails, it
should be possible to boot the affected virtual machines on the other host,
having the last written data available.
It
seems to be the best way to mount the mirrored/replicated disks in both dom0's,
create virtual groups using lvm and export logical devices to the domU's, one
logical device for each virtual machine.
Maybe
it's a good idea then to use clvm to make changes of the virtual groups
possible at runtime. Is there any easy to install and configure alternative to
clvm?
What
is an easy way of mirror and mount both disks in dom0?
As
far as i could see, the best ways are:
A)
DRBD / GNBD / Some kind of shared FS
OR
B)
Export all drives using ISCSI / Create software raid of the same disks in both
dom0's
TO
A):
Can
DRBD handle and replicate simultaneous writes to both drives in primay/primary
mode?
Does
the use of any shared FS always needs a server/client structure? Defining one
of the hosts as the filesystem server creates a single point of failure... Is
this the reason for using heartbeat (to switch the server in case of failure)?
Sound's not like an easy setup...
How
are writes to images handled at a client of the shared fs? Are they sent to the
server and then mirrored back by DRDB? Sound's a bit like waste of ressources,
doesn't it?
Can
You recommend a howto for such a setup?
TO
B)
Is
it possible to have independent software raids of the same both disks in both
dom0's? Raid on host A doesn't recognizes writes to the disks from host B,
doe's it? Maybe i misunderstood the setup...
Can
a software raid be configured to read only from the local disk and write to all
disks (to improve performance)?
Can
You recommend a howto for such a setup?
Can
You recommend any other setup?
Thank
You,
Marc
