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This patch series implement qcow2 external snapshot support for files && lvm
volumes
The current internal qcow2 snapshots have a lot of performance problems.
I have tested through nfs and also local filesystem
https://lore.proxmox.com/pve-devel/6a44716a-88bc-4523-b210-d67031917...@proxmox.com/t/
I see that Fiona don't have same result than me, but I got something like
200~300iops
vs 20000 iops with 4k randwrite when a snapshot exist.
The result is even worst on a shared filesystem like ocfs2 or gfs2. (around 80
iops)
I think (I'm not 100% sure) this is mostly because metadatas are not
preallocated
anymore with qcow2 internal snap.
With external snapshot, I almost don't have any performance impact when a
snapshot exist.
Also other bugs are freeze/lock reported by users since years on snapshots
delete on nfs
https://forum.proxmox.com/threads/snapshot-removal-jams-the-vm.111648/
(The disk access seem to be frozen during all the delete duration)
External qcow2 snapshots also allow snapshot of raw devices ,so 0 performance
impact without snapshots.
This also open doors for remote snapshot export-import for storage replication.
This V2 introduce support for qcow2 external snapshot for lvm, extra lvm
volume is created for each snapsphot and formated with qcow2.
This is a lot more performant than lvm (non-thin/nomedata) snapshot, and allow
to use
it for shared lvm. (I have another patch series for thick lvm dynamic extend,
but if we could have at minimum
snapshot working, it could great :)
I have tested: snasphot, snap rollback, snap delete, clone, move disk, rename
disk, create_base. (online && offline)
lxc is not yet supported, but I think we could look to implement the recent
dm-qcow2 kernel block driver
https://lore.kernel.org/lkml/164846619932.251310.3668540533992131988.stgit@pro/T/
storage.cfg example:
dir: local2
path /var/liv/vz
content snippets,vztmpl,backup,images,iso,rootdir
snapext 1
lvmqcow2:test
vgname test
snapext 1
content images
changelog v2:
implement lvm with external qcow2 snapshots
pve-storage:
Alexandre Derumier (2):
add external snasphot support
add lvmqcow2 plugin: (lvm with external qcow2 snapshot)
src/PVE/Storage.pm | 2 +
src/PVE/Storage/DirPlugin.pm | 1 +
src/PVE/Storage/LvmQcow2Plugin.pm | 460 ++++++++++++++++++++++++++++++
src/PVE/Storage/Makefile | 3 +-
src/PVE/Storage/Plugin.pm | 225 +++++++++++++--
5 files changed, 665 insertions(+), 26 deletions(-)
create mode 100644 src/PVE/Storage/LvmQcow2Plugin.pm
qemu-server:
Alexandre Derumier (1):
implement external snapshot
PVE/QemuServer.pm | 108 ++++++++++++++++++++++++++++++++++++++++------
1 file changed, 95 insertions(+), 13 deletions(-)
--
2.39.2
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