Am Mittwoch, 30. November 2016, 10:38:08 CET schrieb Roman Mamedov: > On Wed, 30 Nov 2016 00:16:48 +0100 > > Wilson Meier <wilson.me...@gmail.com> wrote: > > That said, btrfs shouldn't be used for other then raid1 as every other > > raid level has serious problems or at least doesn't work as the expected > > raid level (in terms of failure recovery). > > RAID1 shouldn't be used either: > > *) Read performance is not optimized: all metadata is always read from the > first device unless it has failed, data reads are supposedly balanced > between devices per PID of the process reading. Better implementations > dispatch reads per request to devices that are currently idle. > > *) Write performance is not optimized, during long full bandwidth sequential > writes it is common to see devices writing not in parallel, but with a long > periods of just one device writing, then another. (Admittedly have been > some time since I tested that). > > *) A degraded RAID1 won't mount by default. > > If this was the root filesystem, the machine won't boot. > > To mount it, you need to add the "degraded" mount option. > However you have exactly a single chance at that, you MUST restore the RAID > to non-degraded state while it's mounted during that session, since it > won't ever mount again in the r/w+degraded mode, and in r/o mode you can't > perform any operations on the filesystem, including adding/removing > devices. > > *) It does not properly handle a device disappearing during operation. > (There is a patchset to add that). > > *) It does not properly handle said device returning (under a > different /dev/sdX name, for bonus points). > > Most of these also apply to all other RAID levels.
So the stability matrix would need to be updated not to recommend any kind of BTRFS RAID 1 at the moment? Actually I faced the BTRFS RAID 1 read only after first attempt of mounting it "degraded" just a short time ago. BTRFS still needs way more stability work it seems to me. -- Martin -- 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
