Re: [Xen-users] cluster filesystems

[Andrej Radonic <andrej.radonic@xxxxxxxx>]

Peter Fokkinga wrote:
> Quoting Brock Edward Palen <brockp@xxxxxxxxx>:
> > Ive just been reading on ocfs2 and a lwn article
> > http://lwn.net/Articles/137278/
> > 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.
Peter,
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.

Cheers,
Andrej


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