RE: [Xen-users] Xen and GFS

["Stephen Palmer" <spalmer@xxxxxxxxxxxxxxxxxxx>]

Oh, well, I guess the difference is that I'm not actually mounting the
files as VBD's (as I innacurately said earlier).  I'm just using the
syntax:

disk = [ 'file:/mnt/xen/vrserver1,xvda,w' ]

... to do file backed storage.  They're never attached as VBD's to DomU.
Maybe that would work for you?

-Steve

> -----Original Message-----
> From: Jim Klein [mailto:jklein@xxxxxxxxxxxxxxxx]
> Sent: Tuesday, April 18, 2006 3:58 PM
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Cc: Stephen Palmer
> Subject: 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
> >>
> >> _______________________________________________
> >> Xen-users mailing list
> >> Xen-users@xxxxxxxxxxxxxxxxxxx
> >> http://lists.xensource.com/xen-users


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