[Lustre-discuss] Upgrading From Lustre 1.4 to 1.8

[Andreas Dilger]

On 2010-06-10, at 14:21, Adam wrote:
>>> I'm curious if it 
>>> would/should also work with an older version of Lustre like 1.4.
>> 
>> Yes, a rolling upgrade from (perhaps only later versions of) 1.4 to 1.6
>> should work and then a rolling upgrade from 1.6 to 1.8.
>> 
>> I would consider trying to upgrade from 1.4 to 1.8 a very risky, and
>> likely-to-fail, proposition.
> 
> That's what seems so great about the idea of a rolling-upgrade, if you 
> have enough spare hardware to do it, then a 1.4 and 1.8 environment can 
> be made available for testing at the same time. If the 1.8 set fails 
> then no worries, flip back to the 1.4 set, then try again by downgrading 
> the 1.8 set to 1.6.

Note that the network protocols between 1.4 and 1.8 are not compatible, so you cannot do a rolling upgrade.  The on-disk data format (excluding the configuration files) is compatible, so in theory it should be possible to run the 1.4->1.6 upgrade process, mount the OST/MDT once and do a quick client test, and then go immediately to 1.8.

> Is there risk in terms of something destructive that 1.8 might try to do 
> to a component of the LFS?

If you go through 1.6 (even if only briefly) it should update the on-disk configuration appropriately, and then the upgrade to 1.8 should work cleanly, and (in theory) it should still be possible to downgrade to 1.4 if needed.  That said, I'd recommend trying this first and/or making a backup (which are always good to have).

Cheers, Andreas
--
Andreas Dilger
Lustre Technical Lead
Oracle Corporation Canada Inc.