Bug#659762: lvm2: LVM commands freeze after snapshot delete fails

[Nikola Kotur]

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This was almost a show-stopper for me.

If you want use LVM snapshots until this bug is fixed, there are only
two options.

1) Low level logical volume management

Remove the snapshot from the device mapper before actually removing it:

dmsetup remove YOUR_VG-snap1
dmsetup remove YOUR_VG-snap1-cow

Then you'll be able to lvremove it without making your server useless.
But this looks and feels dirty. Better to...

2) Use thin provisioning [1]

And get arbitrary depth of recursive snapshots for free :)

Seriously, this bug does not exist if you use thin provisioning. Try
this (if your kernel supports it):

Create thin pool first:

lvcreate --size 300M --type thin-pool --thinpool thin_pool YOUR_VG

Create volume:

lvcreate -V4G -T YOUR_VG/thin_pool --name lv1

Then create and and remove snapshot many times:

for i in {1..200000}; do lvcreate -L4G -n snap1
- --snapshot /dev/YOUR_VG/lv1 ; lvremove -f /dev/YOUR_VG/snap1 ; done

[1] -
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/device-mapper/thin-provisioning.txt?id=refs/tags/v3.9-rc2

- -- 
Nikola Kotur

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