Re: [Xen-users] Xen and GFS

[Jim Klein <jklein@xxxxxxxxxxxxxxxx>]

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
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users