Hi Zdenek,
Thank you for your patience and explanations. I learned a lot from our
discussions and thank you again for your help.
Regards
Zhiyong
On 1/10/23 6:18 AM, Zdenek Kabelac wrote:
Dne 09. 01. 23 v 7:21 Zhiyong Ye napsal(a):
Hi Zdenek,
Thank you for your detailed answer.
For the thin snapshot I will use the latest version of kernel and lvm
for further testing. I want to use both snapshot methods (thin and
thick) in the production environment. But if the thick snapshot is
only still in the maintenance phase, then for thick lv I have to see
if there is any other way to accomplish the snapshot function.
FYI - there are still some delays with up-streaming of the latest
improvement patches - so stay tuned for further speedup gains & IO
throughput with thin provisioning)
By the maintenance phase for old thick snapshot I mean - the development
of the existing thick snapshot target is basically done - the format is
very ancient and cannot be changed without major rewrite of the whole
snapshot target as such - and that's what we've made with newly
introduced thin-provisioning target which addressed many shortcomings of
the old dm-snapshot target.
I use lvm mainly for virtualized environments. Each lv acts as a block
device of the virtual machine. So I also consider using qemu's own
snapshot feature. When qemu creates a snapshot, the original image
used by the virtual machine becomes read-only, and all write changes
are stored in the new snapshot. But currently qemu's snapshots only
support files, not block devices.
Depending on the use-case it might matter to pick the best fitting
chunk-size.
i.e. if the changes are 'localized' in the filesystem areas to match
thin-pool chunks (also selection of the filesystem itself might be part
of equation here) - even if you use snapshots a lot, you may eventually
get better result with bigger chunks like 128k or even 256k size instead
of default 64K.
Regards
Zdenek
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