[linux-lvm] Restore data from a Invalid Snapshot or COW.

[Oliver Carreño]

Dear friends,
Performing a system upgrade, I lost important data from a logical volume. The
only thing I have to retrieve that data is a snapshot inactive, because the
COW out of space in the update. When I try to mount the snapshot, I get I / O
errors. And if I try to mount the partition COW, this show me unknown file
system  error.

¿I can extract data from a snapshot invalid or Cow?
Thanks and regards.


# dmsetup status
eBox--Veneyarna-swap_1: 0 20209664 linear
eBox--Veneyarna-root-real: 0 550223872 linear
eBox--Veneyarna-rootsnap: 0 550223872 snapshot Invalid
eBox--Veneyarna-backups: 0 104857600 linear
eBox--Veneyarna-rootsnap-cow: 0 419430400 linear
eBox--Veneyarna-root: 0 550223872 snapshot-origin



# dmsetup table
eBox--Veneyarna-swap_1: 0 20209664 linear 8:5 550224256
eBox--Veneyarna-root-real: 0 550223872 linear 8:5 384
eBox--Veneyarna-rootsnap: 0 550223872 snapshot 252:0 252:2 P 16
eBox--Veneyarna-backups: 0 104857600 linear 8:17 384
eBox--Veneyarna-rootsnap-cow: 0 419430400 linear 8:17 104857984
eBox--Veneyarna-root: 0 550223872 snapshot-origin 252:0

# vgdisplay
  /dev/dm-3: read failed after 0 of 4096 at 0: Input/output error
  --- Volume group ---
  VG Name               eBox-Veneyarna
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  23
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                4
  Open LV               1
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               737.25 GiB
  PE Size               4.00 MiB
  Total PE              188735
  Alloc PE / Size       133633 / 522.00 GiB
  Free  PE / Size       55102 / 215.24 GiB
  VG UUID               IB3AdY-85sg-p5El-L1Er-qpB3-0BWI-LvYmYj

# lvdisplay
  /dev/dm-3: read failed after 0 of 4096 at 0: Input/output error
  --- Logical volume ---
  LV Name                /dev/eBox-Veneyarna/root
  VG Name                eBox-Veneyarna
  LV UUID                FhcR2z-aouw-X6wg-BKsz-wNdX-QwvS-KWZoiV
  LV Write Access        read/write
  LV snapshot status     source of
                         /dev/eBox-Veneyarna/rootsnap [INACTIVE]
  LV Status              available
  # open                 0
  LV Size                262.37 GiB
  Current LE             67166
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:1

  --- Logical volume ---
  LV Name                /dev/eBox-Veneyarna/swap_1
  VG Name                eBox-Veneyarna
  LV UUID                Czx0Yi-1NCA-Ejwv-i0S2-I1yW-amD8-eV6KY8
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                9.64 GiB
  Current LE             2467
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:4

  --- Logical volume ---
  LV Name                /dev/eBox-Veneyarna/backups
  VG Name                eBox-Veneyarna
  LV UUID                5uWOv8-mwp2-utqI-QtAC-rbH3-GejG-zcWY4n
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                50.00 GiB
  Current LE             12800
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:5

  --- Logical volume ---
  LV Name                /dev/eBox-Veneyarna/rootsnap
  VG Name                eBox-Veneyarna
  LV UUID                HQ0HGG-31Mq-IZR1-3LDy-WIMG-BrAa-IhVpIN
  LV Write Access        read/write
  LV snapshot status     INACTIVE destination for /dev/eBox-Veneyarna/root
  LV Status              available
  # open                 0
  LV Size                262.37 GiB
  Current LE             67166
  COW-table size         200.00 GiB
  COW-table LE           51200
  Snapshot chunk size    8.00 KiB
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:3


Oliver Carreño
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