[lustre-discuss] migrating MDS to different infrastructure

[Mohr Jr, Richard Frank (Rick Mohr)]

> On Aug 22, 2018, at 8:10 PM, Riccardo Veraldi <Riccardo.Veraldi at cnaf.infn.it> wrote:
> 
> On 8/22/18 3:13 PM, Mohr Jr, Richard Frank (Rick Mohr) wrote:
>>> On Aug 22, 2018, at 3:31 PM, Riccardo Veraldi <Riccardo.Veraldi at cnaf.infn.it> wrote:
>>> I would like to migrate this virtual machine to another infrastructure. it is not simple because the other infrastructure is vmware.
>>> what is the best way to migrate those partitions without incurring into any corruption of data ?
>>> May I simply use zfs send and zfs receive thru SSH ?
>>> what is the best way to move a MDS based virtual machine ?
>> I don’t have much experience with VMs, but I have used zfs send/receive to migrate a MDT from one server to another.  It worked quite well.
> that's encouraging. it should work for VM too then regardless.
> I have many MDSes as virtual machines. I found it to be a good way for high availability, they perform well enough.
> 
> so what  you do is to shut down lustre on OSSes and MDS. At this point you simply zfs send and zfs receive on the new MDS ?
> once the operation is terminated the new MDS is just ready to be used ?

It is possible to take snapshots on the current MDT and do incremental send/receives to the new MDT while the system is still up and running.  When you are ready to switch over, then you shutdown the file system, do a final send/receive, and then start the new MDS.  The new MDS will need to have the same configuration (NID, etc.) as the old MDS (unless you want to perform a writeconf).

There was a talk at LUG in 2017 from someone who did something similar with OSTs:

http://cdn.opensfs.org/wp-content/uploads/2017/06/Wed06-CroweTom-lug17-ost_data_migration_using_ZFS.pdf

That should give you a good idea of how to proceed.

--
Rick Mohr
Senior HPC System Administrator
National Institute for Computational Sciences
http://www.nics.tennessee.edu