On 2019-12-02 14:22, Nathan Fish wrote:
You may be thinking of "lazytime". "relatime" only updates atime when updating mtime, to prevent being inconsistent.
I was thinking about the behaviour of relatime on kernels since 2.6.30 (quoting mount(8)): -------------------- "Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than the current modify or change time. (Similar to noatime, but it doesn't break mutt or other applications that need to know if a file has been read since the last time it was modified.) Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the file's last access time is always updated if it is more than 1 day old." -------------------- This also matches RedHats documentation for RHEL 6 and up: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/power_management_guide/relatime And it also matches what I observe for a local ext4 e.g. on Ubuntu 18.04: -------------------- # mount /dev/sda7 on /var type ext4 (rw,relatime,data=ordered) # stat /var/log/gpu-manager.log ... Access: 2019-09-20 18:26:12.713360857 +0200 Modify: 2019-11-20 01:11:11.594634547 +0100 Change: 2019-11-20 01:11:11.594634547 +0100 # cat /var/log/gpu-manager.log > /dev/null # stat /var/log/gpu-manager.log ... Access: 2019-12-02 14:28:20.643034594 +0100 Modify: 2019-11-20 01:11:11.594634547 +0100 Change: 2019-11-20 01:11:11.594634547 +0100 -------------------- I would also be fine with lazytime, though, but does ceph-fuse support it? Cheers, Oliver
On Mon, Dec 2, 2019 at 4:46 AM Oliver Freyermuth <freyermuth@xxxxxxxxxxxxxxxxxx> wrote: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 _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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