[Lustre-discuss] Proper shutdown sans clients

[Dilger, Andreas]

There is no particular danger to the filesystem if clients fail to unmount. Clients have no direct ability to modify filesystem metadata, so they should never be able to corrupt the filesystem.  This is no different than if clients crash or if the network fails, or whatever else bad happens to large computers on a regular basis. 

If the MDT(s) are unmounted first then the OSTs it at least avoids one smal bit of recovery. If you know that the clients will not be coming back (e.g. power outage and servers are running on UPS) then "umount -f" of the servers will evict all of the clients immediately and it will avoid recovery when they are remounted.  The same can be achieved at mount time with "-o abort_recov". 

If you are doing some minor administration on the server, normal "umount" is enough, and allows the clients to recover and possibly complete their IO after the servers have restarted.

For major releases (e.g. 1.8 to 2.x) the clients need to unmount cleanly or will be automatically be evicted after the upgrade.

Cheers, Andreas

On 2013-10-22, at 8:52, "K. Scott Rowe" <krowe at nrao.edu> wrote:

> 
> We use Lustre 1.8.7.  Our environment has many Lustre clients spread
> out accross several networks.  When an emergency happes, like a power
> outage, where we need to quickly shutdown the Lustre servers we
> frequently are unable to shutdown the clients first.  I know that the
> documentation recommends shutting down Lustre in this order:
> 
>  unmount clients
>  unmount MDT
>  unmount OSTs
> 
> So my question is, what would the recommended procedure be if one
> cannot shutdown all the clients first?  Would it just be
> 
>  unmount MDT
>  unmount OSTs
> 
> Or is there something else that should be done because we cannot get
> the clients shutdown first?
> 
> --
> K. Scott Rowe -- Linux Grouop Lead
> Array Operations Center, National Radio Astronomy Observatory
> krowe at nrao.edu -- http://www.aoc.nrao.edu/~krowe/
> 1.575.835.7000 -- 1003 Lopezville Socorro, NM 87801 
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