[lustre-devel] Recommendation for hsm_restore for directories

Degremont, Aurelien degremoa at amazon.fr
Thu Nov 25 02:18:15 PST 2021

Hello all

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.

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.
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.

Do you have any recommendation on the right way to frame this directory access for copytools?


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