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* [linux-lvm] Question about vgreduce on raid lvm cache
@ 2019-11-29  8:35 Heming Zhao
  2020-01-03  3:10 ` Heming Zhao
  0 siblings, 1 reply; 2+ messages in thread
From: Heming Zhao @ 2019-11-29  8:35 UTC (permalink / raw)
  To: linux-lvm

Hello list,

I met a lvm cache issue recently.

The machine had an LVM VG configured with:
  dev1 + dev2 -> data_lv with raid 1 mirror
  dev3 + dev4 -> data_cache_lv with raid 1 mirror and type cache

These were assembled to a cached volume with:
"lvconvert --type cache --cachemode writeback --cachepool data/data_cache_lv data/data_lv"

The device dev4 then died and was removed from the system.

When attempting to remove the device using "vgreduce --removemissing", lvm removed both data_cache_lv and data_lv from the data vg.

This is unexpected behaviour, as dev1, dev2, dev3 were all still present.
The expected behaviour should:
vgreduce --removemissing
lvconvert -m0 system/lv

When it's a non-cached type, and you performe vgreduce, lvs are NOT removed.

the (reproduced) command list:
pvcreate /dev/mapper/dev1 /dev/mapper/dev2 /dev/mapper/dev3 /dev/mapper/dev4
vgcreate VG /dev/mapper/dev1 /dev/mapper/dev2 /dev/mapper/dev3 /dev/mapper/dev4
lvcreate --type raid1 -m 1 -L150 -n data_lv VG /dev/mapper/dev1 /dev/mapper/dev2
lvcreate --type raid1 -m 1 -L150 -n data_cache_lv VG /dev/mapper/dev3 /dev/mapper/dev4
lvconvert --type cache --cachemode writeback --cachepool VG/data_cache_lv VG/data_lv
dmsetup remove -f dev4
vgreduce --removemissing --force VG


^ permalink raw reply	[flat|nested] 2+ messages in thread

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2019-11-29  8:35 [linux-lvm] Question about vgreduce on raid lvm cache Heming Zhao
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