> I would say it is, but I also don't have quite as much experience with it as > with BTRFS raid1 mode. The one thing I do know for certain about it is that > even if it theoretically could recover from two failed disks (ie, if they're > from different positions in the striping of each mirror), there is no code > to actually do so, so make sure you replace any failed disks as soon as > possible (or at least balance the array so that you don't have a missing > device anymore).
Ok, so that really speaks for raid1... > Most of my systems where I would run raid10 mode are set up as BTRFS raid1 > on top of two LVM based RAID0 volumes, as this gets measurably better > performance than BTRFS raid10 mode at the moment (I see roughly a 10-20% > difference on my home server system), and provides the same data safety > guarantees as well. It's worth noting for such a setup that the current > default block size in BTRFS is 16k except on very small filesystems, so you > may want a larger stripe size than you would on a traditional filesystem. > > As far as BTRFS raid10 mode in general, there are a few things that are > important to remember about it: > 1. It stores exactly two copies of everything, any extra disks just add to > the stripe length on each copy. > 2. Because each stripe has the same number of disks as it's mirrored > partner, the total number of disks in any chunk allocation will always be > even, which means that if your using an odd number of disks, there will > always be one left out of every chunk. This has limited impact on actual > performance usually, but can cause confusing results if you have differently > sized disks. > 3. BTRFS (whether using raid10, raid0, or even raid5/6) will always try to > use as many devices as possible for a stripe. As a result of this, the > moment you add a new disk, the total length of all new stripes will adjust > to fit the new configuration. If you want maximal performance when adding > new disks, make sure to balance the rest of the filesystem afterwards, > otherwise any existing stripes will just stay the same size. Those are very good things to know! -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
