[lustre-discuss] new lustre setup, questions about the mgt and mdt.

[Harr, Cameron]

I'd second what Daniel said. Each of our MDS nodes has one zpool with 
one mdt, except the first MDS node also has an mgs dataset on the pool. 
The nodes are set up in failover pairs where each can see each other's 
zpool and import them if necessary (with MMP protection turned on).


On 10/23/2018 12:58 PM, Daniel Kobras wrote:
> Hi!
>
>> Am 23.10.2018 um 19:36 schrieb Kurt Strosahl <strosahl at jlab.org>:
>>
>> 1) I've seen it said that ZFS is a good choice for the lustre mdt, as long as it is zfs 0.7.x.  Has anyone had that experience?
>> 2) What about the MGT, that seems like it wouldn't have any issues with being on zfs.
> We’ve been running several all-ZFS backed systems over the last few years. Way back in the 2.5 days, there once was a ZFS-specific issue with ACLs that we’ve actually hit in production. Other than that, the backend FS never caused any problems—or they were insignificant enough to slip my mind.
>
>> The system I presently have in mind is two servers hooked up to a jbod, with the MDT and the MGT being separate zpools on the jbod.  That way one head to run the mgt and one could run the mdt, while allowing both heads to serve as the backup for each other.
> MGS data is small, mostly static, and in my experience, the extra load from the service can be neglected as well. So overall you’re probably better off if you don’t waste drives on a separate pool just for the MGS. Just add them to the MDT pool instead, and enjoy the extra oomph. Or consider splitting the drivesl into two pools for an active/active configuration with one MDT on each node instead. Depending on how your workload spreads across multiple MDTs, this can be beneficial even for a relatively small number of disks because you effectively double your cache size.
>
> Kind regards,
>
> Daniel
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