[Lustre-discuss] Lustre failback

[Brian J. Murrell]

On Thu, 2008-06-26 at 19:09 +0530, trupti shete wrote:
> Hi 
> 
>       Can anybody tell me that whether lustre does a failback? 

That depends on what you are using to control failover/failback.

> Means I want to ask that, if MDS1 (the primary MDS) fails MDS2 ( which
> is a failover MDS ) will do the work on behalf of MDS1, but what will
> happen if MDS1 is up again? Will it start working as primary MDS
> again? Or will MDS2 continue to work?

Failover/failback are controlled by a process external to Lustre.
Failover is achieved most simply by powering off a node in failure (to
be absolutely sure of no multi-mounts of the MDT) and mounting the MDT
on the partner.  When the primary comes back, it MUST NOT mount the MDT
while secondary has it mounted.  The secondary can then unmount the MDT
and the master mount it.

Nothing in Lustre controls this unmounting and mounting however.  That
is the job of software like Linux Heartbeat.

b.

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