[Lustre-discuss] forced umount of OST in failover case?

[Sheila Barthel]

Andreas -

I just opened BZ 15854 to track this update to the Lustre manual. It 
will be included in the next edition.

Sheila

Andreas Dilger wrote:
> On May 19, 2008  13:09 -0700, Nathaniel Rutman wrote:
>   
>> Erich Focht wrote:
>>     
>>> the lustre manual says:
>>>
>>>  2.2.1.5 Stopping a Server
>>>  To stop a server:
>>>  $ umount -f /mnt/test/ost0
>>>  The '-f' flag means "force"; force the server to stop WITHOUT RECOVERY. 
>>>  Without the '-f' flag, "failover" is
>>>  implied, meaning the next time the server is started it goes through the 
>>>  recovery procedure.
>>>
>>> So we were tempted to use "umount -f" when doing a failover of OSTs, but we
>>> see problems (I/O errors on clients) during the failover when doing this.
>>> Without the "-f" flag we get no I/O errors.
>>>       
>>   
>> yes.  That is the difference between "forced" or not.  Forced means stop 
>> with errors for clients, unforced means take more time and do recovery 
>> at restart.
>>     
>>> Is there a recommended way of dealing with the umount at failover?
>>>   
>>>       
>> Don't use -f
>>     
>
> Perhaps it makes sense to clarify the manual a bit?  It doesn't really
> make sense to have the manual specify "-f" as the default action, IMHO,
> since this isn't what 99% of users or scripts will do.
>
> Something like:
>
> To stop a server:
>
> # umount /mnt/test/ost0
>
> This preserves the state of the connected clients, and the next time the
> server is started it will wait for clients to reconnect and go through
> the recovery procedure.
>
> If the '-f' ("force") flag is given, the server will evict all clients and
> stop WITHOUT RECOVERY.  The server will not wait for recovery upon restart.
> Any currently connected clients will get IO errors until they reconnect.
>
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
>
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