Willy Tarreau wrote:
At work, we had the same problem on a file server with ext3. We use rsync to make backups to a local IDE disk, and we noticed that getdents() took about the same time as Peter reports (0.2 to 2 seconds), especially in maildir directories. We tried many things to fix it with no result, including enabling dirindexes. Finally, we made a full backup, and switched over to XFS and the problem totally disappeared. So it seems that the filesystem matters a lot here when there are lots of entries in a directory, and that ext3 is not suitable for usages with thousands of entries in directories with millions of files on disk. I'm not certain it would be that easy to try other filesystems on kernel.org though :-/
Changing filesystems would mean about a week of downtime for a server. It's painful, but it's doable; however, if we get a traffic spike during that time it'll hurt like hell.
However, if there is credible reasons to believe XFS will help, I'd be inclined to try it out.
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