[Lustre-discuss] Deactivate OST

[Brian J. Murrell]

On Thu, 2009-09-24 at 11:31 +0200, Frank Heckes wrote:
> Hi all,

Hi,

> sorry if this has been answered before, but I could find only one
> un-answered question concerning this topic in the archive.

Hrm.  Strange, as I believe this has been answered in the archive many,
many times.  I believe the answer to this is in the manual too.

> If I like to deactivate write operation for an OST temporary, but allow
> clients to read still data from the OST, disabling the OST on the MDS
> will do the job as described in the admin guide.

Not quite.  Disabling on the MDS only disables "new allocation", not
write.  That means that new objects won't be allocated to files from the
deactivated OST.  Writes to existing objects will still be allowed.

> In case an OST was lost and clients shouldn't contact the OST anymore
> (if OST is damaged irreversible) even for read operation, could I
> execute the 'lcl --device <id> deactivate' command also on the clients?

Hrm.  I usually fiddle with the proc file directly on this, but suffice
it to say that whatever operation you are using on the MDS to deactivate
an OST can be used on the client to return EIOs when a given OST is
accessed.

> Or is this action superfluous since the client will receive EIO's
> anyway?

No.  The client will only receive EIOs if that client has deactivated
the OST.

> Many thanks in advance.

NP.

b.

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