[lustre-discuss] Questions about migrate OSTs from ldiskfs to zfs

[Dilger, Andreas]

On Mar 2, 2016, at 01:18, Alexander I Kulyavtsev <aik at fnal.gov<mailto:aik at fnal.gov>> wrote:

Please see inlined.

On Feb 26, 2016, at 6:36 PM, Dilger, Andreas <andreas.dilger at intel.com<mailto:andreas.dilger at intel.com>> wrote:

On Feb 23, 2016, at 05:24, Fernando Perez <fperez at icm.csic.es<mailto:fperez at icm.csic.es>> wrote:

Hi all.
... snip...

- Dou you recommend to do a lustre update before replace the OSTs by the new zfs OSTs?

Lustre 2.4.1 is very old.  It makes sense to use a newer version than this, especially if you are using ZFS.

However, it is generally bad sysadmin practice to do major hardware and software updates at the same time, since it becomes very difficult to isolate any problems that appear afterward. I would recommend to upgrade to a newer version of Lustre (2.5.3, or what is recommended from your support provider) at least on the servers and run that for a week or two before doing the hardware upgrade.
is tag 2.5.3.90 considered stable?

The .90 release is the first release in code freeze before making the 2.5.4 release. I think this one is reasonably good.

- I have read in the list that there are problem with the last zfsonlinux release and lustre only works with zfsonlinux 0.6.3. Is this right?

Newer versions of Lustre work well with ZFS 0.6.4.3, I don't remember anymore what ZFS versions were tested with 2.4.1. We had some problems under heavy load with 0.6.5.3 and have moved back to 0.6.4.3 for the Lustre 2.8.0 release until that is fixed.
We are 0.6.4.2, the last before 0.6.5.1.
What is zfs 0.6.4.3 ?

My bad. I was mixing this up with 0.6.5.3 (which is now 0.6.5.4). In any case, there was a major patch landed in the 0.6.5 release that caused occasional problems with Lustre and is still under investigation.

https://github.com/zfsonlinux/zfs/issues/4210

It only hits under significant system load, so it may not affect everyone.

Cheers, Andreas