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xen-users
Re: [Xen-users] Xen and GFS
That's exactly what I want to do, and I am using FC5 as well. But
when I create the VBD's (either with the xenguest-install.py script
or manually creating an img file with dd and mounting -o loop) I get
I/O errors and the messages in the log listed earlier. The images
mount, but are not writable, presumably because of a locking problem.
I found a note in the kernel archives that spoke of problems getting
loop file systems to mount properly off a GFS volume, but didn't see
a resolution.
On Apr 18, 2006, at 1:42 PM, Stephen Palmer wrote:
I've done exactly this (with iSCSI instead of FC), but I did take the
extra step to configure GFS, as I intended each cluster node to run
various DomU's (3 or 4 on each). The DomU VBD's are all stored on the
same iSCSI LUN, so each node can read/write to the LUN simultaneously
with GFS.
It took a lot of trial and error to get everything working - I got
stuck
trying to figure out why the LVM2-cluster package was missing in
Fedora
Core 5, and finally realized that it wasn't really necessary as
long as
I did all of the LVM administration from one node and used the
pvscan/vgscan/lvscan tools on the other nodes to refresh the metadata.
Stephen Palmer
Gearbox Software
CIO/Director of GDS
-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of John Madden
Sent: Tuesday, April 18, 2006 3:31 PM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Cc: Jim Klein
Subject: Re: [Xen-users] Xen and GFS
On Tuesday 18 April 2006 16:17, Jim Klein wrote:
The setup I have is 3 - AMD_64DP server blades w/ 4Gb RAM each,
attached to FC SAN. The thought was that I would create a GFS volume
on the SAN, mount it under Xen dom0 on all 3 blades, create all the
VBDs for my VMs on the SAN, and thus be able to easily migrate VMs
from one blade to another, without any intermediary mounts and
unmounts on the blades. I thought it made a lot of sense, but maybe
my approach is wrong.
Not necessarily wrong, but perhaps just an unnecessary layer. If
your
intent
is HA Xen, I would set it up like this:
1) Both machines connected to the SAN over FC
2) Both machines having visibility to the same SAN LUN(s)
3) Both machines running heartbeat with private interconnects
4) LVM lv's (from dom0) on the LUN(s) for carving up the storage for
the
domU's
5) In the event of a node failure, the failback machine starts with
an "/etc/init.d/lvm start" or equivalent to prep the lv's for use.
Then
xend
start, etc.
For migration, you'd be doing somewhat the same thing, only you'd
need
a
separate SAN LUN (still use LVM inside dom0) for each VBD. My
understanding
is that writing is only done by one Xen stack at once (node 0 before
migration, node 1 after migration, nothing in between), so all you
have to
do
is make that LUN available to the other Xen instance and you
should be
set.
A cluster filesystem should only be used when more than one node must
write
to the same LUN at the same time.
John
--
John Madden
Sr. UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@xxxxxxxxxxx
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