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

[Damir Krstic]

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.

So at this point in time, we either have ESS built with 4.1 version and
cross mount its filesystem (also built with --version flag I assume) to our
3.5 compute cluster, or...we proceed with 4.2 ESS and build filesystems
with --version flag and then in June when we get all of our clients upgrade
we run =latest gpfs command and then mmchfs -V to get filesystem back up to
4.2 features.

It's unfortunate that we are in this bind with the downtime of the compute
cluster. If we were allowed to upgrade our compute nodes before June, we
could proceed with 4.2 build without having to worry about filesystem
versions.

Thanks for your reply.

Damir

On Wed, Mar 16, 2016 at 12:18 PM Sven Oehme <oehmes at gmail.com> wrote:

> while this is all correct people should think twice about doing this.
> if you create a filesystem with older versions, it might prevent you from
> using some features like data-in-inode, encryption, adding 4k disks to
> existing filesystem, etc even if you will eventually upgrade to the latest
> code.
>
> for some customers its a good point in time to also migrate to larger
> blocksizes compared to what they run right now and migrate the data. i have
> seen customer systems gaining factors of performance improvements even on
> existing HW by creating new filesystems with larger blocksize and latest
> filesystem layout (that they couldn't before due to small file waste which
> is now partly solved by data-in-inode). while this is heavily dependent on
> workload and environment its at least worth thinking about.
>
> sven
>
>
>
> On Wed, Mar 16, 2016 at 4:20 PM, Marc A Kaplan <makaplan at us.ibm.com>
> wrote:
>
>> The key point is that you must create the file system so that is "looks"
>> like a 3.5 file system.  See mmcrfs ... --version.  Tip: create or find a
>> test filesystem back on the 3.5 cluster and look at the version string.
>>  mmslfs xxx -V.  Then go to the 4.x system and try to create a file system
>> with the same version string....
>>
>>
>> [image: Marc A Kaplan]
>>
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>>
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