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Hi Luke,
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<div class="">I’ve got an off the wall suggestion for you, which may or may not work depending on whether or not you have any UID conflicts with old and new UIDs … this won’t actually speed things up but it will eliminate the “downtime” for your users. And
the big caveat is that there can’t be any UID conflicts … i.e. someone’s new UID can’t be someone else’s old UID.</div>
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<div class="">Given that … what if you set an ACL to allow access to both their old and new UIDs … then change their UID to the new UID … then chown the files to the new UID and remove the ACL? More work for you, but no downtime for them.</div>
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<div class="">We actually may need to do something similar as we will need to change Windows-assigned UID’s based on SIDs to “correct” UIDs at some point in the future on one of our storage systems.</div>
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<div class="">If someone has a better way to solve your problem, I hope they’ll post it to the list, as it may help us as well. HTHAL. Thanks…</div>
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<div class="">Kevin</div>
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<div class="">On Jun 30, 2017, at 10:20 AM, <a href="mailto:hpc-luke@uconn.edu" class="">
hpc-luke@uconn.edu</a> wrote:</div>
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<div class="">Hello, <br class="">
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<span class="Apple-tab-span" style="white-space:pre"></span>We're trying to change most of our users uids, is there a clean way to<br class="">
migrate all of one users files with say `mmapplypolicy`? We have to change the<br class="">
owner of around 273539588 files, and my estimates for runtime are around 6 days.<br class="">
<br class="">
<span class="Apple-tab-span" style="white-space:pre"></span>What we've been doing is indexing all of the files and splitting them up by<br class="">
owner which takes around an hour, and then we were locking the user out while we<br class="">
chown their files. I made it multi threaded as it weirdly gave a 10% speedup<br class="">
despite my expectation that multi threading access from a single node would not<br class="">
give any speedup.<br class="">
<br class="">
<span class="Apple-tab-span" style="white-space:pre"></span>Generally I'm looking for advice on how to make the chowning faster. Would<br class="">
spreading the chowning processes over multiple nodes improve performance? Should<br class="">
I not stat the files before running lchown on them, since lchown checks the file<br class="">
before changing it? I saw mention of inodescan(), in an old gpfsug email, which<br class="">
speeds up disk read access, by not guaranteeing that the data is up to date. We<br class="">
have a maintenance day coming up where all users will be locked out, so the file<br class="">
handles(?) from GPFS's perspective will not be able to go stale. Is there a<br class="">
function with similar constraints to inodescan that I can use to speed up this<br class="">
process?<br class="">
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Thank you for your time,<br class="">
<br class="">
Luke<br class="">
Storrs-HPC<br class="">
University of Connecticut<br class="">
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<div class="">—</div>
<div class="">Kevin Buterbaugh - Senior System Administrator</div>
<div class="">Vanderbilt University - Advanced Computing Center for Research and Education</div>
<div class=""><a href="mailto:Kevin.Buterbaugh@vanderbilt.edu" class="">Kevin.Buterbaugh@vanderbilt.edu</a> - (615)875-9633</div>
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