Hi,
with multiple active MDS daemons you can use pinning. This allows you
to pin specific directories (or subvolumes) to a specific rank to
spread the load. You can find the relevant docs here [0].
Note that during an upgrade, max_mds is reduced to 1 (automatically if
you use the orchestrator), which can have a significant impact because
all the load previously spreaded across multiple daemons is now
shuffled onto a single node. This can crash a file system, just so
you're aware.
So there are several options, two or three "fat" MDS nodes in
active/standby mode which can handle all the load. Or you have more
"fat" nodes which could handle all the load during an upgrade,
spreading the load again after the upgrade is finished. Or you have
multiple "not so fat" nodes to spread the workload but with a higher
risk of an issue during an upgrade.
Regards,
Eugen
[0] https://docs.ceph.com/en/latest/cephfs/multimds/
[1]
https://docs.ceph.com/en/latest/cephfs/upgrading/#upgrading-the-mds-cluster
Zitat von Sophonet <[email protected]>:
Hi list,
for multiple project-level file shares (with individual access
rights) I am planning to use CephFS.
Technically this can be implemented both with multiple toplevel
cephfs or with a single cephfs in the cluster and subvolumes.
What is the preferred choice? I have not found any guidance in
docs.ceph.com <http://docs.ceph.com/>. The only location that
suggests to use subvolumes is
https://www.ibm.com/docs/en/storage-ceph/8.1.0?topic=systems-cephfs-volumes-subvolumes-subvolume-groups. However, how can I avoid that only one MDS is responsible for serving all subvolumes? Is there some current literature (books or web docs) that contain recommendations and examples? A couple of ceph-related books are available in well-known online book stores, but many of them are rather old (6 years or even
more).
Thanks a lot,
Sophonet
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