wiki:TipAndDoc/storage/LVM

Version 19 (modified by mitty, 10 years ago) (diff)

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  1. LVM RAID
    1. LVM with MD-RAID
  2. Thin provisioning
    1. metadata
    2. /etc/lvm/lvm.conf
      1. error_when_full

LVM RAID

  • ​https://wiki.gentoo.org/wiki/LVM#Different_storage_allocation_methods

    It is not possible to stripe an existing volume, nor reshape the stripes across more/less physical volumes, nor to convert to a different RAID level/linear volume. A stripe set can be mirrored. It is possible to extend a stripe set across additional physical volumes, but they must be added in multiples of the original stripe set (which will effectively linearly append a new stripe set).

    • RAID1,4,5,6でreshapeなどが使えないのは結構厳しい制限に思える。MD-RAIDでは可能なので、そのうちサポートされるかも知れない

LVM with MD-RAID

  • ​mdadm と LVM で作る、全手動 BeyondRAID もどき - 守破離

    ざっくり言うと、RAID1 か RAID5 でHDDを横断する領域をいくつか作って、その領域をまとめあげる事で大容量のストレージを作る感じですね。 これのイケてる点は HDD が 1 台消えても大丈夫な上に、状況によっては HDD を 1 台交換するだけでストレージの容量がアップすること。 最低 2 台の HDD を大容量の物に交換すれば確実に容量が増えます。

Thin provisioning

  • ​(CentOS) LVM thinpool snapshots broken in 6.5?

    For the people who run into this as well: This is apparently a feature and not a bug. Thin provisioning snapshots are no longer automatically activated and a "skip activation" flag is set during creation by default. One has to add the "-K" option to "lvchange -ay <snapshot-volume>" to have lvchange ignore this flag and activate the volume for real. "-k" can be used on lvcreate to not add this flag to the volume. See man lvchange/lvcreate for more details. /etc/lvm/lvm.conf also contains a "auto_set_activation_skip" option now that controls this.

    Apparently this was changed in 6.5 but the changes were not mentioned in the release notes.

    • thin snapshotはデフォルトではinactiveで作成され、activateするにはlvchangeに'-K'オプションが必要となった('-k y -K'とするのが良さそう)
  • 現時点(ArchLinux 4.0.1-1-ARCH, lvm2 2.02.116-1)では、thin poolは拡張は出来るが縮小は出来ない
    • # lvextend -l100%VG vg/pool0 
        Size of logical volume vg/pool0_tdata changed from 2.00 GiB (512 extents) to 2.59 GiB (663 extents).
  Logical volume pool0 successfully resized
    • # lvreduce -L2.5G vg/pool0 
        Thin pool volumes cannot be reduced in size yet.
  Run `lvreduce --help' for more information.

metadata

  • ​http://man7.org/linux/man-pages/man7/lvmthin.7.html metadataを直接操作する方法なども記述されている
  • ​(linux-lvm) how to recover after thin pool metadata did fill up? 古いバージョンのlvm2ではmetadataのリサイズが出来ない模様
  • ​dm-thin: issues about resize the pool metadata size
    • metadataを大幅に大きくしようとすると失敗する事例 (3.12.0-rc7, lvm2 2.02.103)
    • ArchLinux 4.0.1-1-ARCH, lvm2 2.02.116-1では、オンラインで問題なく拡張可能
      1. # lvs -a 
          pool0           vg   twi-aotz--   2.00g              98.44  26.46
  [pool0_tdata]   vg   Twi-ao----   2.00g
  [pool0_tmeta]   vg   ewi-ao----   4.00m
      2. lvextend -L+128M vg/pool0_tmeta 
          Size of logical volume vg/pool0_tmeta changed from 4.00 MiB (1 extents) to 132.00 MiB (33 extents).
  Logical volume pool0_tmeta successfully resized

        May 10 15:50:06 raid-test kernel: device-mapper: thin: 252:2: growing the metadata device from 1024 to 33792 blocks
      3. # lvs -a 
          pool0           vg   twi-aotz--   2.00g              98.44  0.81
  [pool0_tdata]   vg   Twi-ao----   2.00g
  [pool0_tmeta]   vg   ewi-ao---- 132.00m

/etc/lvm/lvm.conf

error_when_full

  • 0 (default)
    • thin poolが一杯になると、書き込みはキューイングされる。thin poolはout-of-data-space modeになる 
      May 10 12:35:10 raid-test lvm[303]: Thin vg-pool0-tpool is now 96% full.
May 10 12:40:36 raid-test kernel: device-mapper: thin: 252:2: reached low water mark for data device: sending event.
May 10 12:40:36 raid-test kernel: device-mapper: thin: 252:2: switching pool to out-of-data-space mode
May 10 12:40:36 raid-test lvm[303]: Thin vg-pool0-tpool is now 100% full.
    • #l vs -a -o+lv_when_full 
        LV              VG   Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert WhenFull
  lv1             vg   Vwi-aotz--   3.00g pool0        66.67
  pool0           vg   twi-aotzD-   2.00g              100.00 25.98                            queue
    • (デフォルトでは)60秒、thin poolが拡張されるのを待ち、失敗するとファイルシステムへエラーを返す。thin poolは read-only modeになる 
      May 10 12:41:36 raid-test kernel: device-mapper: thin: 252:2: switching pool to read-only mode
May 10 12:41:36 raid-test kernel: EXT4-fs warning (device dm-8): ext4_end_bio:317: I/O error -5 writing to inode 17 (offset 25165824 size 8388608 starting block 591856)
May 10 12:41:36 raid-test kernel: buffer_io_error: 38109 callbacks suppressed
May 10 12:41:36 raid-test kernel: Buffer I/O error on device dm-8, logical block 591856
May 10 12:41:36 raid-test kernel: EXT4-fs warning (device dm-8): ext4_end_bio:317: I/O error -5 writing to inode 17 (offset 25165824 size 8388608 starting block 591857)
May 10 12:41:36 raid-test kernel: Buffer I/O error on device dm-8, logical block 591857

(snip)

May 10 12:41:36 raid-test kernel: device-mapper: thin: 252:2: metadata operation 'dm_pool_commit_metadata' failed: error = -1
May 10 12:41:36 raid-test kernel: device-mapper: thin: 252:2: aborting current metadata transaction
May 10 12:41:36 raid-test kernel: device-mapper: thin: 252:2: switching pool to read-only mode
    • # lvs -a -o+lv_when_full 
        LV              VG   Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert WhenFull
  lv1             vg   Vwi-aotz--   3.00g pool0        66.67
  pool0           vg   twi-aotzM-   2.00g              100.00 25.98                            queue
    • read-onlyから復旧するには、全てのthin LVをinactivate -> thin pool LVをinactivate -> lvconvert --repair thinpoolLV する必要がある
  • 1
    • thin poolが一杯になると、書き込みは即座に失敗する。 
      May 10 12:53:17 raid-test kernel: device-mapper: thin: 252:2: reached low water mark for data device: sending event.
May 10 12:53:17 raid-test kernel: device-mapper: thin: 252:2: switching pool to out-of-data-space mode
May 10 12:53:17 raid-test kernel: EXT4-fs warning (device dm-8): ext4_end_bio:317: I/O error -28 writing to inode 17 (offset 33554432 size 8388608 starting block 591872)
May 10 12:53:17 raid-test kernel: buffer_io_error: 39292 callbacks suppressed
May 10 12:53:17 raid-test kernel: Buffer I/O error on device dm-8, logical block 591872
May 10 12:53:17 raid-test kernel: EXT4-fs warning (device dm-8): ext4_end_bio:317: I/O error -28 writing to inode 17 (offset 33554432 size 8388608 starting block 591873)

(snip)

May 10 12:53:17 raid-test lvm[303]: Thin vg-pool0-tpool is now 100% full.
May 10 12:53:27 raid-test kernel: EXT4-fs warning: 135366 callbacks suppressed
May 10 12:53:27 raid-test kernel: EXT4-fs warning (device dm-8): ext4_end_bio:317: I/O error -28 writing to inode 17 (offset 588054528 size 4857856 starting block 727248)
May 10 12:53:27 raid-test kernel: buffer_io_error: 135366 callbacks suppressed

(snip)
    • # lvs -a -o+lv_when_full 
        lv1             vg   Vwi-aotz--   3.00g pool0        66.67
  pool0           vg   twi-aotzD-   2.00g              100.00 26.86                            error
    • fstrimなどを用いて、割り当てを解放すると、すぐに復旧する 
      May 10 12:55:29 raid-test kernel: device-mapper: thin: 252:2: switching pool to write mode
May 10 12:55:29 raid-test kernel: device-mapper: thin: 252:2: switching pool to write mode
    • # lvs -a -o+lv_when_full 
        lv1             vg   Vwi-aotz--   3.00g pool0        65.62
  pool0           vg   twi-aotz--   2.00g              98.44  26.46                            error
  • オンラインで即座に変更可能
    • # lvchange --errorwhenfull y vg/pool0 
        Logical volume "pool0" changed.

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