[Lustre-discuss] manual OST failover for maintenance work?

[Kevin Van Maren]

Cliff White wrote:
> On 12/06/2010 09:57 AM, Adeyemi Adesanya wrote:
>   
>> Hi.
>>
>> We have pairs of OSS nodes hooked up to shared storage arrays
>> containing OSTs but we have not enabled any failover settings yet. Now
>> we need to perform maintenance work on an OSS and we would like to
>> minimize Lustre downtime. Can I use tunefs.lustre to specify the OSS
>> failover NID for an existing OST? I assume i'll have to take the OST
>> offline to make this change. Will clients that have Lustre mounted
>> pick up this change or will all clients have to remount? I should
>> mention that we are running Lustre 1.8.2.
>>     
>
>
> Yes, see the Lustre Manual for details.
> cliffw
>   

Should be something like this for an OST:
# tunefs.lustre --writeconf --erase-params --mgsnode=10.0.0.1 at o2ib 
--mgsnode=10.0.0.2 at o2ib --param="failover.node=10.0.1.2 at o2ib" /dev/ost0

Do MGS first (if not already done and it will have failover).  Dedicated 
mgs should not have to specify mgs, just the failover.
For MDT, would probably have to also have 
--param="mdt.group_upcall=/usr/sbin/l_getgroups"

Note that you must add the failover NID (ie, do the tunefs and the first 
mount) on the _primary_ (non-failover) node.

Lustre machines get the NID information for MDT/OST devices from the MGS 
at mount time.
There is no callback mechanism to notify of changes to the NIDs, so yes, 
clients would
have to re-mount the file system to be able to use the failover NIDs.

Kevin