[lustre-discuss] migrating MDS to different infrastructure

[Riccardo Veraldi]

it is time for me to move my MDS to a diferent HW infrastructure.
So I Was wondering if the following procedure can work.
I have mds1 (old mds) and mds2 (new mds). On the old mds I have a zfs 
MGS partition and a zfs MDT partition.

  * create a new ZFS  MGS and MDT partition on mds2 and create a lustre
    FS on it
  * umount lustre on mds2
  * stop all the OSSes belonging to mds1 and stop and umount lustre on mds1
  * zfs send the MGS partition from mds1 and zfs receive it on mds2
  * zfs send the MGT partition from mds1 and zfs receive it on mds2
  * mount lustre on mds2

should it work ?

thanks

Rick


On 8/23/18 2:40 PM, Mohr Jr, Richard Frank (Rick Mohr) wrote:
>> 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
>

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