[lustre-discuss] lustre_rsync with growing statuslog

Andreas Dilger adilger at whamcloud.com
Fri May 20 16:32:03 PDT 2022

On May 20, 2022, at 06:33, Robert Redl <robert.redl at lmu.de<mailto:robert.redl at lmu.de>> wrote:

Dear Lustre Experts,

since a few weeks we are keeping two Lustre system synchronous using lustre_rsync. That works fine, but the statuslog file is growing. It is currently about 500MB in size. Updating it is apparently slowing down the whole process.

Is it only important to keep the statuslog in cases where lustre_rsync has been interrupted? Or is it necessary to keep it forever in order to not miss any changes.

It should be noted that lustre_rsync is not commonly used and only tested in the context of an automated regression test that runs and largely passes.  It was developed originally as a proof of concept for Lustre Changelogs, so may be missing support for newer features (e.g. explicit file layouts, project IDs, ACLs, etc, though that *may* all be handled by rsync).  There may be unknown bugs lurking in this code, so use with some caution (i.e. don't sync your bank transaction records with it).

I would recommend to at least use some other tool (e.g. MPIFileUtils) to periodically do a full scan to verify that the files are being copied over properly to the target filesystem.

Taking a quick look into the lustre_rsync.c, I see that "statuslog" appears to be a log file of pending rename actions, or something like that?  It is backed up when lustre_rsync is started, but only to a file <statuslog>.old.  It looks like an entry is added into "parents" if it is renamed to/from a directory that doesn't exist in the target, but I don't know enough detail to say why that isn't working properly in your case.

Feedback, patches, and status updates are welcome.  Maybe you can present about your usage of it at LAD this year?  I don't want to totally discourage your usage of lustre_rsync since it has potential for further improvements (e.g. parallel copying, bug fixing, etc), otherwise it will never get better, but just wanted to make sure you know what the current state of this tool.

Cheers, Andreas
Andreas Dilger
Lustre Principal Architect

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