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On Nov 24, 2021, at 10:33, Degremont, Aurelien via lustre-devel <<a href="mailto:lustre-devel@lists.lustre.org" class="">lustre-devel@lists.lustre.org</a>> wrote:<br class="">
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<div class="">Hello all<br class="">
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I'm doing some early work toward implementing a directory/namespace support for Lustre/HSM. The idea would be to support something similar to hsm_restore/hsm_release but for directories.<br class="">
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My first thought was for the MDT to not grant LDLM lock for this directory and hold it, while the directory is getting restored by copytool, in a similar fashion than what is done for files. But the hard part here, is to have a way for copytool to access the
directory while its access is actually prevented by the above locking.<br class="">
Restoring a file is using this smart trick of restoring it in a different temporary file and using layout swap at the end to move data to the actual real file. It looks difficult to do the same thing here.<br class="">
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Do you have any recommendation on the right way to frame this directory access for copytools?<br class="">
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<div>I've thought about this in the past, and IMHO the best way to handle a directory or directory tree would be to save the directory and/or whole tree in an ldiskfs image rather than a tarball. The reasoning for this is that in the future it would allows
directly mounting the image for access by the MDT and/or client (Client Container Image), unlike a tarball that needs to be extracted each time before use.</div>
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<div>There is some discussion about this in <a href="https://jira.whamcloud.com/browse/LU-13024" class="">
https://jira.whamcloud.com/browse/LU-13024</a></div>
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<div>Cheers, Andreas</div>
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<div>Andreas Dilger</div>
<div>Lustre Principal Architect</div>
<div>Whamcloud</div>
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