PVE 5 - lvs reports reports wrong %Snap size for thin LV


Mar 9, 2010

I have a freshly upgraded pve 5 installation, and I think there's something wrong in lvs command output for thin lv.

When i call lvs command with option for showing snapshot sizes , the output reports Snap% equal to Data% for thin provisioned volumes (last two columns). I have no snapshot currently.

# lvs -o+size,data_percent,snap_percent
  LV               VG       Attr       LSize   Pool         Origin Data%  Meta%  Move Log Cpy%Sync Convert LSize   Data%  Snap%
  .drbdctrl_0      drbdpool -wi-ao----   4,00m                                                               4,00m            
  .drbdctrl_1      drbdpool -wi-ao----   4,00m                                                               4,00m            
  drbdthinpool     drbdpool twi-aotz--   1,56t                     61,16  31,23                              1,56t 61,16  61,16
  vm-100-disk-2_00 drbdpool Vwi-aotz--  10,00g drbdthinpool        99,99                                    10,00g 99,99  99,99
  vm-101-disk-1_00 drbdpool Vwi-aotz--   4,00g drbdthinpool        99,93                                     4,00g 99,93  99,93
  vm-101-disk-2_00 drbdpool Vwi-aotz--  60,02g drbdthinpool        100,00                                   60,02g 100,00 100,00
  vm-102-disk-1_00 drbdpool Vwi-aotz--  12,00g drbdthinpool        99,99                                    12,00g 99,99  99,99
  vm-103-disk-1_00 drbdpool Vwi-aotz--  10,01g drbdthinpool        99,91                                    10,01g 99,91  99,91
  vm-103-disk-2_00 drbdpool Vwi-aotz--   5,01g drbdthinpool        99,88                                     5,01g 99,88  99,88
  vm-104-disk-1_00 drbdpool Vwi-aotz--  10,00g drbdthinpool        86,28                                    10,00g 86,28  86,28
  vm-104-disk-2_00 drbdpool Vwi-aotz-- 900,20g drbdthinpool        93,52                                   900,20g 93,52  93,52
  vm-106-disk-1_00 drbdpool Vwi-a-tz--   8,01g drbdthinpool        0,00                                      8,01g 0,00   0,00
  vm-121-disk-1_00 drbdpool Vwi-aotz--  15,02g drbdthinpool        99,92                                    15,02g 99,92  99,92
  vm-122-disk-1_00 drbdpool Vwi-aotz--   8,01g drbdthinpool        85,68                                     8,01g 85,68  85,68
  vm-123-disk-1_00 drbdpool Vwi-aotz--   5,01g drbdthinpool        99,88                                     5,01g 99,88  99,88
  data             pve      -wi-ao----  16,82g                                                              16,82g            
  root             pve      -wi-ao----   7,25g                                                               7,25g            
  swap             pve      -wi-ao----   2,00g                                                               2,00g
I'm deeply impacted by this, because onboard DRBD9 is using these thinlv as backend, and a terse version of this command is issued by drbdmanage to calculate free space. Obiouvsly the sum of Data + Snap space is more than 100% , leaving no free space.

I tested the same command on another machine with PVE 4 on board
LVM version: 2.02.116(2) (2015-01-30), kernel: 4.4.35-1-pve
and the %Snap column is empty

My context:
# lvs --version
  LVM version:     2.02.168(2) (2016-11-30)
  Library version: 1.02.137 (2016-11-30)
  Driver version:  4.35.0

# uname -r

# pveversion -v
proxmox-ve: 5.0-20 (running kernel: 4.10.17-2-pve)
pve-manager: 5.0-30 (running version: 5.0-30/5ab26bc)
pve-kernel-4.10.17-2-pve: 4.10.17-20
libpve-http-server-perl: 2.0-6
lvm2: 2.02.168-pve3
corosync: 2.4.2-pve3
libqb0: 1.0.1-1
pve-cluster: 5.0-12
qemu-server: 5.0-15
pve-firmware: 2.0-2
libpve-common-perl: 5.0-16
libpve-guest-common-perl: 2.0-11
libpve-access-control: 5.0-6
libpve-storage-perl: 5.0-14
pve-libspice-server1: 0.12.8-3
vncterm: 1.5-2
pve-docs: 5.0-9
pve-qemu-kvm: 2.9.0-4
pve-container: 2.0-15
pve-firewall: 3.0-2
pve-ha-manager: 2.0-2
ksm-control-daemon: 1.2-2
glusterfs-client: 3.8.8-1
lxc-pve: 2.0.8-3
lxcfs: 2.0.7-pve4
criu: 2.11.1-1~bpo90
novnc-pve: 0.6-4
smartmontools: 6.5+svn4324-1


Mar 9, 2010
Having studied a little how thin provisioning works, it seems to me that drbdmanage thin_lv plug in code is wrong. No need to sum Snap%, the Data% of the pool accounts for all allocated space.

Sorry for the noise.



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