• [v6.9-b1] Revert to using df to get free space for btrfs pools

    JorgeB

    By JorgeB (edited)

      • Minor

    I believe it was used before but due to unreliable values it stopped being used, on newer kernels it should work reliably, and better than current method for some situations.

     

    There are frequent posts on the forum from users using two different size devices in a pool, because free space is incorrectly reported and they run out of it, e.g. a pool made of 32GB + 64GB devices default raid1

     

    image.png.5a7ed4d7c36cf482bf59e72fac0451d4.png

     

    Usable space will be around 32GB, GUI reports 47GB, df reports correctly:

     

    image.png.9b0f196dce55cd2f1587c87555d6608a.png

     

    Also starting with even newer kernels, like the one on v6.9-beta1 it started correctly reporting free space for raid5/6 profiles, pool made of four 64GB devices using raid6

     

    image.png.ca3686cbd4a39499d1b66218f7934022.png

     

    With df:

     

    image.png.607207dc0bcffa550f1c900005766cb1.png

     

    Please change this for v6.9, with multiple pools it will likely affect more users.

     

     

    Edited by johnnie.black

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    limetech

    Code uses the 'statfs()' call which returns

    f_blocks - total blocks

    f_bfree - free blocks in filesystem

    f_bavail - free blocks available to unprivileged user

     

    and we are reporting f_bfree.  We used to report f_bavail (which I think is what it should be) but that didn't work for btrfs; however, in running some tests, it seems it now does report correctly, so that change has been made in next release (beta23).

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