[gpfsug-discuss] cross-cluster mounting different versions of gpfs

[Jonathan Buzzard]

On 16/03/16 18:07, Damir Krstic wrote:
> Sven,
>
> For us, at least, at this point in time, we have to create new
> filesystem with version flag. The reason is we can't take downtime to
> upgrade all of our 500+ compute nodes that will cross-cluster mount this
> new storage. We can take downtime in June and get all of the nodes up to
> 4.2 gpfs version but we have users today that need to start using the
> filesystem.
>

You can upgrade a GPFS file system piece meal. That is there should be 
no reason to take the whole system off-line to perform the upgrade. So 
you can upgrade a compute nodes to GPFS 4.2 one by one and they will 
happily continue to talk to the NSD's running 3.5 while the other nodes 
continue to use the file system.

In a properly designed GPFS cluster you should also be able to take 
individual NSD nodes out for the upgrade. Though I wouldn't recommend 
running mixed versions on a long term basis, it is definitely fine for 
the purposes of upgrading.

Then once all nodes in the GPFS cluster are upgraded you issue the 
mmchfs -V full. How long this will take will depend on the maximum run 
time you allow for your jobs.

You would need to check that you can make a clean jump from 3.5 to 4.2 
but IBM support should be able to confirm that for you.

This is one of the nicer features of GPFS; its what I refer to as 
"proper enterprise big iron computing". That is if you have to take the 
service down at any time for any reason you are doing it wrong.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Fife, United Kingdom.