Dear Cephers,

we are currently mounting CephFS with relatime, using the FUSE client (version 
13.2.6):
  ceph-fuse on /cephfs type fuse.ceph-fuse 
(rw,relatime,user_id=0,group_id=0,allow_other)

For the first time, I wanted to use atime to identify old unused data. My expectation 
with "relatime" was that the access time stamp would be updated less often, for 
example,
only if the last file access was >24 hours ago. However, that does not seem to 
be the case:

----------------------------------------------
$ stat 
/cephfs/grid/atlas/atlaslocalgroupdisk/rucio/group/phys-higgs/ed/cb/group.phys-higgs.17620861._000004.HSM_common.root
...
Access: 2019-04-10 15:50:04.975959159 +0200
Modify: 2019-04-10 15:50:05.651613843 +0200
Change: 2019-04-10 15:50:06.141006962 +0200
...
$ cat 
/cephfs/grid/atlas/atlaslocalgroupdisk/rucio/group/phys-higgs/ed/cb/group.phys-higgs.17620861._000004.HSM_common.root
 > /dev/null
$ sync
$ stat 
/cephfs/grid/atlas/atlaslocalgroupdisk/rucio/group/phys-higgs/ed/cb/group.phys-higgs.17620861._000004.HSM_common.root
...
Access: 2019-04-10 15:50:04.975959159 +0200
Modify: 2019-04-10 15:50:05.651613843 +0200
Change: 2019-04-10 15:50:06.141006962 +0200
...
----------------------------------------------

I also tried this via an nfs-ganesha mount, and via a ceph-fuse mount with 
admin caps,
but atime never changes.
Is atime really never updated with CephFS, or is this configurable?

Something as coarse as "update at maximum once per day only" would be perfectly 
fine for the use case.

Cheers,
        Oliver

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature

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