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Re: [Xen-users] cluster filesystems

Peter Fokkinga wrote:
Quoting Brock Edward Palen <brockp@xxxxxxxxx>:
Ive just been reading on ocfs2 and a lwn article
and makes the comment that its ment to be used: "s meant to operate with a disk which is, itself, shared across the cluster
(perhaps via some sort of storage-area network or multipath scheme)."
So this requires some sort of NAS unit? or does it work like PVFS2 ware each machine has its own local disk holding only a portion of the data?

If you want to share a disk using ocfs2 to multiple _physical_
servers you will probably need a SAN (expensive...) I once
read about sharing a disk between hosts using firewire, but
that's really a hobby solution ;-)

In Xen however it's really simple, you just export a volume
(whether it's a file, a partition or a LVM volume) from dom0
to multiple domU's. It's really not much different than exporting
an ext3 volume. Well, you do need a view ocfs2 processes in each
domU  that talk to each other (tcp, on port 7777) but you
definitely do not need a SAN.
this may be a stupid question but what do you mean by "In Xen it's really simple" as opposed to the SAN approach? OCFS2 is "just" a filesystem, it doesn't seem to be a way of distributing blockdevices via ethernet like NFS does. So what is the point in using OCFS2 in conjunction with Xen without a SAN or iSCSI or multipath infrastructure? If I understood Brock correctly he is looking for a robust and probably high-performance (and cheap) alternative to NFS (I am too...).
Thanks ahead for some "enlightening" thoughts.


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