[lustre-discuss] space is not released when removing files using zfs-0.6.4.2-1 and Lustre 2.8.0

[Crowe, Tom]

Greetings All,

I have come across a strange scenario using zfs 0.6.4.2-1 and Lustre 2.8.0.

In a nutshell, when we delete items from lustre using rm, the files/dirs are seemingly removed, but the space is not freed on the underlying zfs dataset/zpool. We have unmounted the OST/dataset, exported the zpool, and even rebooted the server altogether. The space is never freed.

I have read through many of the issues logged about this on https://github.com/zfsonlinux; many folks have reclaimed the space once they unmount/remount, and/or export/import. As noted above, this has no impact on our dataset/zpool.

We currently have a zpool scrub running, and expect this to complete in the next few hours.

We DO have zfs compression enabled, and we are using ZFS quota and reservations for the associated OST/dataset.

We have copied the dataset to an entirely different zpool (zfs send/receive), and then mounted as native ZFS to poke around. In doing so, we located some of the "broken path" files that were of decent size (4GB) and went a head and removed them with rm. These files were/are ones that we see with the ??? in the path output from zdb. After removing the files, the space was almost immediately freed from the dataset/zpool.

Here is an example of a directory and a file from the zdb output.


    Object  lvl   iblk   dblk  dsize  lsize   %full  type
       136    2    16K    16K  9.00K    32K  100.00  ZFS directory
                                        144   bonus  System attributes
        dnode flags: USED_BYTES USERUSED_ACCOUNTED
        dnode maxblkid: 1
        path    ???<object#136>
        uid     0
        gid     0
        atime   Wed Dec 31 19:00:00 1969
        mtime   Wed Dec 31 19:00:00 1969
        ctime   Wed Dec 31 19:00:00 1969
        crtime  Thu Mar 10 12:04:52 2016
        gen     1020298
        mode    40755
        size    2
        parent  1
        links   1
        pflags  0
        rdev    0x0000000000000000
        Fat ZAP stats:
                Pointer table:
                        1024 elements
                        zt_blk: 0
                        zt_numblks: 0
                        zt_shift: 10
                        zt_blks_copied: 0
                        zt_nextblk: 0
                ZAP entries: 2
                Leaf blocks: 1
                Total blocks: 2
                zap_block_type: 0x8000000000000001
                zap_magic: 0x2f52ab2ab
                zap_salt: 0x3fdbcd9ab9
                Leafs with 2^n pointers:
                          9:      1 *
                Blocks with n*5 entries:
                          0:      1 *
                Blocks n/10 full:
                          1:      1 *
                Entries with n chunks:
                          3:      2 **
                Buckets with n entries:
                          0:    510 ****************************************
                          1:      2 *

                0 = 38711 (type: not specified)
                feb93 = 281474976687710 (type: 15 (invalid))

    Object  lvl   iblk   dblk  dsize  lsize   %full  type
       138    1    16K   128K   128K   128K  100.00  ZFS plain file
                                        220   bonus  System attributes
        dnode flags: USED_BYTES USERUSED_ACCOUNTED
        dnode maxblkid: 0
        path    ???<object#138>
        uid     0
        gid     0
        atime   Wed Dec 31 19:00:00 1969
        mtime   Wed Dec 31 19:00:00 1969
        ctime   Wed Dec 31 19:00:00 1969
        crtime  Thu Mar 10 12:04:52 2016
        gen     1020298
        mode    100644
        size    8
        parent  0
        links   1
        pflags  0
        rdev    0x0000000000000000
        SA xattrs: 76 bytes, 1 entries

                trusted.lma = \000\000\000\000\000\000\000\000\003\000\000\000\002\000\000\000\000\000\000\000\000\000\000\000



Can anyone advise on some next steps troubleshooting, or previous experiences that are similar to ours?

Thanks,
Tom

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