On Mon, Dec 29, 2014 at 02:25:14PM -0600, sys.syphus wrote: > so am I to read that as if btrfs redundancy isn't really functional? > if i yank a member of my raid 1 out in live "prod" is it going to take > a dump on my data?
Eh? Where did that conclusion some from? I said nothing at all about RAID-1, only RAID-10. So, to clarify: In the general case, you can safely lose one device from a btrfs RAID-10. Also in the general case, losing a second device will break the filesystem (with very high probability). In the case I gave below, with an even number of equal sized devices, the second device to be lost *may* allow the data to be recovered with sufficient effort, but the FS in general will probably not be mountable with two missing devices. So, btrfs RAID-10 offers the same *guarantees* as traditional RAID-10. It's generally less effective with the probabilities of the failure modes beyond the guarantee. Hugo. > On Mon, Dec 29, 2014 at 1:04 PM, Hugo Mills <h...@carfax.org.uk> wrote: > > On Mon, Dec 29, 2014 at 01:00:05PM -0600, sys.syphus wrote: > >> oh, and sorry to bump myself. but is raid10 *ever* more redundant in > >> btrfs-speak than raid1? I currently use raid1 but i know in mdadm > >> speak raid10 means you can lose 2 drives assuming they aren't the > >> "wrong ones", is it safe to say with btrfs / raid 10 you can only lose > >> one no matter what? > > > > I think that with an even number of identical-sized devices, you > > get the same "guarantees" (well, behaviour) as you would with > > traditional RAID-10. > > > > I may be wrong about that -- do test before relying on it. The FS > > probably won't like losing two devices, though, even if the remaining > > data is actually enough to reconstruct the FS. > > > > Hugo. > > -- Hugo Mills | emacs: Eighty Megabytes And Constantly Swapping. hugo@... carfax.org.uk | http://carfax.org.uk/ | PGP: 65E74AC0 |
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