On Jul 16, 2007 13:02 +0800, Stuart Midgley wrote:> Is the atime of a file stored on the mds or on an ost? I can imagine
> positive and negatives with both approaches.
Both, to some extent. The OSTs store a "transient" atime that is
updated
when clients do read requests. The permanent atime is written to the MDS
when the file is closed, but only changes the on-disk atime if it is more
than 60s (/proc/fs/lustre/mds/*/max_atime_diff) old. The latest atime wins.
If a setattr comes in, it is updated on both the MDS and OST, allowing
the atime to go backward.
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.