On Tue, Jan 21, 2014 at 07:25:43AM -0500, Austin S Hemmelgarn wrote: > On 2014-01-21 01:42, Sandy McArthur wrote: > > On Mon, Jan 20, 2014 at 7:20 AM, Austin S Hemmelgarn > > <ahferroin7@xxxxxxxxx> wrote: > >> > >> On 2014-01-16 14:23, Toggenburger Lukas wrote: > >>> 3. Improving subvolume handling regarding taking recursive snapshots ( https://btrfs.wiki.kernel.org/index.php/Project_ideas#Take_recursive_snapshots ) and taking snapshots of arbitrary directories ( https://btrfs.wiki.kernel.org/index.php/Project_ideas#Snapshot_arbitrary_directories ) > >> > >> Another option that I would personally love to see would be support for > >> write-mostly devices (that is, devices in a RAID1/RAID10 setup that only > >> get written too unless the data can't be found elsewhere). This would > >> in particular provide an alternative to using bcache/dm-cache (namely an > >> SSD and HDD in RAID1 with the HDD set to write-mostly). > >> Based on the current development focus, I don't think anybody is working > >> on this already (I would be, but I don't have either the time or the > >> skills with kernel programming that would be needed). > > > > Maybe this happens already: Might a similar effect be automatically > > achieved by tracking per-device I/O load averages and distributing > > reads based on the I/O loads of possible read devices? > > > That might be the case, it depends on how the I/O load averages are > calculated. I actually hadn't realized BTRFS did this, I thought it > behaved more like MD RAID (that is, distributing the reads among devices > in a un-weighted round-robin fashion). I think David tried that a while ago, and the benchmarks were actually worse. I'm not sure how much investigation he did into why, though. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- Quidquid latine dictum sit, altum videtur. ---
Attachment:
signature.asc
Description: Digital signature
