On Mon, 12 Dec 2022, Joe Thornber wrote: > We're pleased to announce the first release candidate of v1.0.0 of the > thin-provisioning-tools (which also contains tools for dm-cache and > dm-era). > > # Rust > > This is a complete rewrite of the tools in the Rust language. This switch > was made for three primary reasons: > > # thin_dump/restore retains snapshot sharing > > Another issue with previous versions of the tools is dumping and restoring > thin metadata would have the effect of losing sharing of the metadata > btrees for snapshots. Meaning restored metadata often took up more space, and > in some cases would exceed the 16G metadata limit. This is no longer the case. Hurrah! I've been looking forward to this for a long time... Joe, I seem to remember you had you mentioned the possibility of adding metadata range support for dm-thin in the Linux kernel once the Linux kernel supported Rust. Now that it does, is this still on the roadmap? Relatedly, we had an email conversation sometime about go porting the dm-thin path to handle multi-queue behavior better than it does now. I could not find the thread, but I seem to remember that you said this was already applied to dm-cache. I was considering attempting the port, but it looked complicated so you suggested to wait for Rust in the kernel to get metadata range support before looking at dm-thin. ...So if you have any commentary on the future of dm-thin with respect to metadata range support, or dm-thin performance in general, that I would be very curious about your roadmap and your plans. Thanks again for all your great work on this. -Eric > [note: _data_ sharing was always maintained, this is purely about metadata space usage] > > # thin_metadata_pack/unpack > > These are a couple of new tools that are used for support. They compress > thin metadata, typically to a tenth of the size (much better than you'd > get with generic compressors). This makes it easier to pass damaged > metadata around for inspection. > > # blk-archive > > The blk-archive tools were initially part of this thin-provisioning-tools > package. But have now been split off to their own project: > > https://github.com/jthornber/blk-archive > > They allow efficient archiving of thin devices (data deduplication > and compression). Which will be of interest to those of you who are > holding large numbers of snapshots in thin pools as a poor man's backup. > > In particular: > > - Thin snapshots can be used to archive live data. > - it avoids reading unprovisioned areas of thin devices. > - it can calculate deltas between thin devices to minimise > how much data is read and deduped (incremental backups). > - restoring to a thin device tries to maximise data sharing > within the thin pool (a big win if you're restoring snapshots). > >
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