Re: [PATCH v3 0/4] RAID1 with 3- and 4- copies

[David Sterba <dsterba@suse.cz>]

On Thu, Nov 14, 2019 at 12:13:24AM -0500, Zygo Blaxell wrote:
> On Fri, Nov 01, 2019 at 04:09:08PM +0100, David Sterba wrote:
> > The raid1c34 patches are not intrusive and could be backported on top of
> > 5.3 because all the preparatory work has been merged already.
> 
> Indeed, that's how I ended up testing them.  I couldn't get the 5.4-rc
> kernels to run long enough to do meaningful testing before they locked
> up.  I tested with 5.3.8 + patches.
> 
> I left out the last patch that removes the raid1c3 incompat flag because
> 5.3 didn't have the block group tree code to apply it to.
> 
> I ran my raid1 and raid56 corruption recovery tests modified for raid1c3.
> The first test is roughly:
> 
> 	mkfs.btrfs -draid1c3 -mraid1c3 /dev/vd[bcdef]
> 	mount /dev/vdb /test
> 	cp -a 9GB_data /test
> 	sync
> 	sysctl vm.drop_caches=3
> 	diff -r 9GB_data /test
> 	head -c 9g /dev/urandom > /dev/vdb
> 	head -c 9g /dev/urandom > /dev/vdc
> 	sync
> 	sysctl vm.drop_caches=3
> 	diff -r 9GB_data /test
> 	btrfs scrub start -Bd /test
> 	sysctl vm.drop_caches=3
> 	diff -r 9GB_data /test
> 	btrfs scrub start -Bd /test
> 	sysctl vm.drop_caches=3
> 	diff -r 9GB_data /test
> 
> First scrub reported a lot of corruption on /dev/vdb and /dev/vdc.  Second
> scrub reported no errors.  diff (all instances) reported no differences.
> 
> Second test is:
> 
> 	mkfs.btrfs -draid6 -mraid1c3 /dev/vd[bcdef]
> 	# rest as above...
> 
> Similar results:  first scrub reported many errors as expected.
> Second scrub reported no errors.  No diffs.

Thanks for the tests.