Re: [linux-lvm] The feasibility of implementing an alternative snapshot approach
Zdenek Kabelac <[email protected]>
| Newsgroups | dev.linux.lists.linux-lvm |
|---|---|
| Message-ID | <[email protected]> |
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 _______________________________________________ linux-lvm mailing list [email protected] https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/