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<p>Dear Andreas,</p>
<p>thanks a lot for the explanation! Using lustre_rsync is only a
temporal solution for us. We created a full copy of a lustre
system in a different location using ZFS snapshots. This system
has then been renamed and the idea was to keep it for a limited
time synchronized with the original system. Afterwards the new
system should be used in production. <br>
</p>
<p>With your explanation and a look into the source code, I had now
a closer look to the created statuslog. The entries are almost
exclusively pointing to temporal files. Files that are created and
deleted or moved quickly afterwards. We use the statuslog now to
identify directories that need synchronization using standard
rsync. That works as long as the parent of the element to
synchronize is still available, for other cases periodical
traditional rsync will be necessary. <br>
</p>
<p>Cheers,<br>
Robert<br>
</p>
<div class="moz-cite-prefix">Am 21.05.22 um 01:32 schrieb Andreas
Dilger:<br>
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On May 20, 2022, at 06:33, Robert Redl <<a
href="mailto:robert.redl@lmu.de" class="moz-txt-link-freetext"
moz-do-not-send="true">robert.redl@lmu.de</a>> wrote:
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<div class="">Dear Lustre Experts,<br class="">
<br class="">
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.<br class="">
<br class="">
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.<br
class="">
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<div class="">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).</div>
<div class=""><br class="">
</div>
<div class="">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.</div>
<div class=""><br class="">
</div>
<div class="">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.</div>
<div class=""><br class="">
</div>
<div class="">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.<br class="">
<div class=""><br class="">
<div class="">
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<div>Cheers, Andreas</div>
<div>--</div>
<div>Andreas Dilger</div>
<div>Lustre Principal Architect</div>
<div>Whamcloud</div>
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