Re: How to check which directory has ephemeral pinning set?

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Hi Milind,

super, thanks! That's good enough for me.

Just one stupid question. Will the ephemerally pinned sub-trees will always stay entirely on the same MDS rank? I really want to avoid sub-tree exports for folders under /home etc, meaning also avoiding sub-tree exports for a path like /home/x/y/z.

Thanks and good Sunday.
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14

________________________________________
From: Milind Changire <mchangir@xxxxxxxxxx>
Sent: 09 October 2022 09:24:20
To: Frank Schilder
Cc: ceph-users@xxxxxxx
Subject: Re:  How to check which directory has ephemeral pinning set?

On Sat, Oct 8, 2022 at 7:27 PM Frank Schilder <frans@xxxxxx<mailto:frans@xxxxxx>> wrote:
Hi all,

I believe I enabled ephemeral pinning on a home dir, but I can't figure out how to check that its working. Here is my attempt:

Set the flag:
# setfattr -n ceph.dir.pin.distributed -v 1 /mnt/admin/cephfs/hpc/home

Try to read it:
# getfattr -n ceph.dir.pin.distributed  /mnt/admin/cephfs/hpc/home
/mnt/admin/cephfs/hpc/home: ceph.dir.pin.distributed: No such attribute

This is a known issue for pre-pacific releases.
There's a fix in pacific v16.2.8 and later which returns values of ceph.dir.pin* virtual xattrs correctly.

To try to see if the distributed pin flag has indeed been set, you could try getting an inode dump with:
$ ceph tell mds.0 dump inode <inode_number>

and check for the field export_ephemeral_distributed_pin to get the value of that field for that inode.

However, you might have to iterate through the mds ranks to get the inode if the inode has been identified as *hot* and has been distributed to some other mds.
e.g.
$ ceph tell mds.2 dump inode <inode-number>

You can get the dir inode number with:
$ ls -lid /mnt/admin/cephfs/hpc/home

Similarly, if you iterate through all the immediate subdirs of /mnt/admin/cephfs/hpc/home and get inode dumps, you'll get to know which mds is the auth mds for the inode when you actually get the inode dump from the particular mds rank. The mds from which you get the inode dump is the mds that the node has been distributed to for auth queries and responses.




Hmm. ???

Well, at least the first command might have done something, because this fails:
# setfattr -n ceph.dir.pin.distrid -v 1 /mnt/admin/cephfs/hpc/groups
setfattr: /mnt/admin/cephfs/hpc/groups: Invalid argument

What is the right way to confirm its working?

Thanks and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
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--
Milind

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