Re: [Xen-users] Sharing filesystems between VMs.

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> You can't export the same vbd twice r/w, and maybe not even r/o, I
> forget.  There is just no facility for doing that and AFAIK the
> error you get is saving you from seeing both domains crash.

Exporting twice r/o is fine.  If any running domain has r/w access then it 
won't let you start other domains with either r/o or r/w access.

You *can* put a ! after the 'w' permision to mean "no, really share it 
writeable" to disable the check however you should NEVER do this unless you 
have a cluster aware filesystem.

Basically, because the FS layer usually expects only one kernel to access a 
filesystem, one writer and multiple readers will cause confusion, multiple 
readers will hose your filesystem pretty quickly.

> You need a cluster file system like GFS, OCFS, etc., or just NFS.

Yes, if you want write sharing.  Exporting read only is fine, though.

Cheers,
Mark

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