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Date:	Tue, 21 Oct 2014 13:16:52 +0000
From:	Ronny Egner <ronnyegner@...nyegner-consulting.de>
To:	NeilBrown <neilb@...e.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Andrea Mazzoleni" <amadvance@...il.com>
Subject: Re: What happened with the Patch "New RAID library supporting up to
 six parities"

Hi Neil,


i did a short test and it works so far. Here are my results. Let me know
if you need something more:

(TL;DR: Wonderful patch. Tested with PAR6 (= six parities) and was able to
recover from losing five disks at once.)



The patches apply against 3.14.22 and btrfs-progs 3.12 but not against the
recent 3.18-rc1 and btrfs-progs > 3.12.


	root@...ntu-1204-build:~# btrfs --version
	Btrfs v3.12-dirty
	
	root@...ntu-1204-build:~# uname -a
	Linux ubuntu-1204-build 3.14.22 #3 SMP Tue Oct 21 13:00:08 CEST 2014
x86_64 x86_64 x86_64 GNU/Linux


For the tests i used a VM with 4 GB memory, two cores and 15 disks with
150 GB each. Every disk looked like this:

	root@...ntu-1204-build:~# fdisk /dev/sdi

	Command (m for help): p

	Disk /dev/sdi: 157.3 GB, 157286400000 bytes
	81 heads, 30 sectors/track, 126419 cylinders, total 307200000 sectors
	Units = sectors of 1 * 512 = 512 bytes
	Sector size (logical/physical): 512 bytes / 512 bytes
	I/O size (minimum/optimal): 512 bytes / 512 bytes
	Disk identifier: 0x5b5d7269

	Device Boot      Start         End      Blocks   Id  System
	/dev/sdi1            2048   307199999   153598976   83  Linux


File system created:

	root@...ntu-1204-build:~# mkfs.btrfs -dpar6 -L testpar6 /dev/sdh1
/dev/sdi1 /dev/sdj1 /dev/sdk1 \
		                  /dev/sdl1 /dev/sdm1 /dev/sdn1 /dev/sdo1 /dev/sdp1
/dev/sdq1 /dev/sdr1 \
				  /dev/sds1 /dev/sdt1 /dev/sdu1 /dev/sdv1


	Turning ON incompat feature 'extref': increased hardlink limit per file
to 65536
	Turning ON incompat feature 'par3456': raid support with up to six
parities
	adding device /dev/sdi1 id 2
	adding device /dev/sdj1 id 3
	adding device /dev/sdk1 id 4
	adding device /dev/sdl1 id 5
	adding device /dev/sdm1 id 6
	adding device /dev/sdn1 id 7
	adding device /dev/sdo1 id 8
	adding device /dev/sdp1 id 9
	adding device /dev/sdq1 id 10
	adding device /dev/sdr1 id 11
	adding device /dev/sds1 id 12
	adding device /dev/sdt1 id 13
	adding device /dev/sdu1 id 14
	adding device /dev/sdv1 id 15
	fs created label testpar6 on /dev/sdh1
	nodesize 16384 leafsize 16384 sectorsize 4096 size 2.15TiB
	Btrfs v3.12-dirty


Mount:


	root@...ntu-1204-build:~# mount /dev/sdh1 /mnt

Stats:
	
	root@...ntu-1204-build:~# df -h
	Filesystem                 Size  Used Avail Use% Mounted on
	/dev/mapper/vgroot-lvroot   26G   17G  8.4G  67% /
	none                       4.0K     0  4.0K   0% /sys/fs/cgroup
	udev                       1.6G  4.0K  1.6G   1% /dev
	tmpfs                      331M  1.1M  330M   1% /run
	none                       5.0M     0  5.0M   0% /run/lock
	none                       1.7G     0  1.7G   0% /run/shm
	none                       100M     0  100M   0% /run/user
	/dev/sdh1                  2.2T  2.8M  2.2T   1% /mnt


	Data, single: total=8.00MiB, used=0.00
	Data, PAR6: total=9.00GiB, used=995.16MiB
	System, RAID1: total=8.00MiB, used=16.00KiB
	System, single: total=4.00MiB, used=0.00
	Metadata, RAID1: total=1.00GiB, used=65.59MiB
	Metadata, single: total=8.00MiB, used=0.00

	root@...ntu-1204-build:/mnt# btrfs fi show
	Label: testpar6  uuid: 79d3c5e4-74ce-4464-a509-ef666dcd9073
	Total devices 15 FS bytes used 1.04GiB
	devid    1 size 146.48GiB used 1.02GiB path /dev/sdh1
	devid    2 size 146.48GiB used 1.00GiB path /dev/sdi1
	devid    3 size 146.48GiB used 1.00GiB path /dev/sdj1
	devid    4 size 146.48GiB used 1.00GiB path /dev/sdk1
	devid    5 size 146.48GiB used 1.00GiB path /dev/sdl1
	devid    6 size 146.48GiB used 1.00GiB path /dev/sdm1
	devid    7 size 146.48GiB used 1.00GiB path /dev/sdn1
	devid    8 size 146.48GiB used 1.00GiB path /dev/sdo1
	devid    9 size 146.48GiB used 1.00GiB path /dev/sdp1
	devid    10 size 146.48GiB used 1.00GiB path /dev/sdq1
	devid    11 size 146.48GiB used 1.00GiB path /dev/sdr1
	devid    12 size 146.48GiB used 2.00GiB path /dev/sds1
	devid    13 size 146.48GiB used 2.00GiB path /dev/sdt1
	devid    14 size 146.48GiB used 1.01GiB path /dev/sdu1
	devid    15 size 146.48GiB used 1.01GiB path /dev/sdv1


Metadata and data still ‚single‘? Bug? Nevermind - lets convert it:

	root@...ntu-1204-build:/mnt# btrfs balance start -mconvert=raid1 /mnt
	Done, had to relocate 4 out of 6 chunks

	root@...ntu-1204-build:/mnt# btrfs fi df /mnt
	Data, single: total=8.00MiB, used=0.00
	Data, PAR6: total=9.00GiB, used=1.02GiB
	System, RAID1: total=32.00MiB, used=16.00KiB
	Metadata, RAID1: total=1.00GiB, used=67.83MiB
	
	root@...ntu-1204-build:/mnt# btrfs balance start -dconvert=par6 /mnt
	Done, had to relocate 2 out of 4 chunks

	root@...ntu-1204-build:/mnt# btrfs fi df /mnt
	Data, PAR6: total=9.00GiB, used=1.02GiB
	System, RAID1: total=32.00MiB, used=16.00KiB
	Metadata, RAID1: total=1.00GiB, used=68.72MiB



OK now lets see what happens if we remove on device. Save a MD5SUM before:


	root@...ntu-1204-build:/mnt# md5sum linux-3.14.22.tar
	80af37cdfb2fa2239f79597c914a8c73  linux-3.14.22.tar


(Removed one disk and replace it with a brand new, empty one)




	root@...ntu-1204-build:~# mount /dev/sdh1 /mnt
	mount: wrong fs type, bad option, bad superblock on /dev/sdh1,
	missing codepage or helper program, or other error
	In some cases useful info is found in syslog - try
	dmesg | tail  or so

	root@...ntu-1204-build:~# mount /dev/sdh1 /mnt -o degraded
	root@...ntu-1204-build:~#

	root@...ntu-1204-build:~# btrfs fi show
	Label: testpar6  uuid: 79d3c5e4-74ce-4464-a509-ef666dcd9073
	Total devices 15 FS bytes used 31.42GiB
	devid    1 size 146.48GiB used 4.00GiB path /dev/sdh1
	devid    2 size 146.48GiB used 5.00GiB path /dev/sdi1
	devid    3 size 146.48GiB used 4.00GiB path /dev/sdj1
	devid    4 size 146.48GiB used 4.00GiB path /dev/sdk1
	devid    5 size 146.48GiB used 4.00GiB path /dev/sdl1
	devid    6 size 146.48GiB used 5.00GiB path /dev/sdm1
	devid    7 size 146.48GiB used 4.03GiB path /dev/sdn1
	devid    8 size 146.48GiB used 4.00GiB path /dev/sdo1
	devid    9 size 146.48GiB used 4.00GiB path /dev/sdp1
	devid    10 size 146.48GiB used 4.00GiB path /dev/sdq1
	devid    11 size 146.48GiB used 4.00GiB path /dev/sdr1
	devid    12 size 146.48GiB used 4.03GiB path /dev/sds1
	devid    13 size 146.48GiB used 4.00GiB path /dev/sdt1
	devid    14 size 146.48GiB used 4.00GiB path /dev/sdu1
	devid    15 size 146.48GiB used 4.00GiB path


Lets replace the faulty disk:

	root@...ntu-1204-build:~# btrfs device add /dev/sdv1 /mnt
	root@...ntu-1204-build:~# btrfs device delete missing /mnt

	In /var/log/syslog:

	[  191.442050] BTRFS warning (device sdk1): devid 15 missing
	[  581.367659]  sdv: sdv1
	[  598.009968] BTRFS: device label testpar6 devid 16 transid 63 /dev/sdv1
	[  614.679654] BTRFS info (device sdk1): relocating block group
40865103872 flags 4097
	[  657.889822] BTRFS info (device sdk1): found 64 extents
	[  659.190497] BTRFS info (device sdk1): found 64 extents
	[  659.247765] BTRFS info (device sdk1): relocating block group
31201427456 flags 4097
	[  861.359599] BTRFS info (device sdk1): found 132 extents
	[  862.875521] BTRFS info (device sdk1): found 132 extents
	[  862.973499] BTRFS info (device sdk1): relocating block group
11874074624 flags 4097



After the ‚delete missing‘

	Label: testpar6  uuid: 79d3c5e4-74ce-4464-a509-ef666dcd9073
	Total devices 15 FS bytes used 31.42GiB
	devid    1 size 146.48GiB used 4.00GiB path /dev/sdh1
	. . .
	devid    14 size 146.48GiB used 4.00GiB path /dev/sdu1
	devid    16 size 146.48GiB used 4.00GiB path /dev/sdv1


The md5 checksum is still correct:

	root@...ntu-1204-build:/mnt# md5sum linux-3.14.22.tar
	80af37cdfb2fa2239f79597c914a8c73  linux-3.14.22.tar









Hardcore test: PAR6 = 6 parities. Let´s see what happens if i remove five
disks and replace with with empty ones.

Before i did that the metadata format was converted to PAR6 as well:

	
	root@...ntu-1204-build:~# btrfs fi df /mnt/
	Data, PAR6: total=36.00GiB, used=31.32GiB
	System, PAR6: total=144.00MiB, used=16.00KiB
	Metadata, PAR6: total=1.12GiB, used=101.81MiB




	root@...ntu-1204-build:~# mount /dev/sdn1 /mnt/ -o degraded
	

	root@...ntu-1204-build:~# btrfs fi show
	Label: testpar6  uuid: 79d3c5e4-74ce-4464-a509-ef666dcd9073
	Total devices 15 FS bytes used 31.42GiB
	devid    1 size 146.48GiB used 4.00GiB path
	devid    2 size 146.48GiB used 5.00GiB path
	devid    3 size 146.48GiB used 4.00GiB path
	devid    4 size 146.48GiB used 4.00GiB path
	devid    5 size 146.48GiB used 4.00GiB path
	devid    6 size 146.48GiB used 5.00GiB path /dev/sdm1
	devid    7 size 146.48GiB used 4.03GiB path /dev/sdn1
	devid    8 size 146.48GiB used 4.00GiB path /dev/sdo1
	devid    9 size 146.48GiB used 4.00GiB path /dev/sdp1
	devid    10 size 146.48GiB used 4.00GiB path /dev/sdq1
	devid    11 size 146.48GiB used 4.00GiB path /dev/sdr1
	devid    12 size 146.48GiB used 4.03GiB path /dev/sds1
	devid    13 size 146.48GiB used 4.00GiB path /dev/sdt1
	devid    14 size 146.48GiB used 4.00GiB path /dev/sdu1
	devid    16 size 146.48GiB used 4.00GiB path /dev/sdv1


Now let´s bring it back in shape and add five new, empty disks:

	btrfs device add /dev/sdh1 /dev/sdi1 /dev/sdj1 /dev/sdk1 /dev/sdl1 /mnt
	btrfs delete missing
	<<wait>>
	root@...ntu-1204-build:~# btrfs fi show
	Label: testpar6  uuid: 79d3c5e4-74ce-4464-a509-ef666dcd9073
	Total devices 15 FS bytes used 1.09GiB
	devid    6 size 146.48GiB used 2.14GiB path /dev/sdm1
	devid    7 size 146.48GiB used 2.14GiB path /dev/sdn1
	devid    8 size 146.48GiB used 2.14GiB path /dev/sdo1
	devid    9 size 146.48GiB used 2.14GiB path /dev/sdp1
	devid    10 size 146.48GiB used 2.14GiB path /dev/sdq1
	devid    11 size 146.48GiB used 2.14GiB path /dev/sdr1
	devid    12 size 146.48GiB used 2.14GiB path /dev/sds1
	devid    13 size 146.48GiB used 2.14GiB path /dev/sdt1
	devid    14 size 146.48GiB used 2.14GiB path /dev/sdu1
	devid    16 size 146.48GiB used 2.14GiB path /dev/sdv1
	devid    17 size 146.48GiB used 2.14GiB path /dev/sdh1
	devid    18 size 146.48GiB used 2.14GiB path /dev/sdi1
	devid    19 size 146.48GiB used 2.14GiB path /dev/sdj1
	devid    20 size 146.48GiB used 2.14GiB path /dev/sdk1
	devid    21 size 146.48GiB used 2.14GiB path /dev/sdl1





And now the checksum:

	root@...ntu-1204-build:/mnt# md5sum linux-3.14.22.tar
	80af37cdfb2fa2239f79597c914a8c73  linux-3.14.22.tar

Checksum matches! 

So.. this looks *very* good to me.








Mit freundlichen Grüßen
Ronny Egner
--
Ronny Egner
Oracle Certified Master 11g (OCM)
 
Mobile:   +49 170 8139903
EMail:      ronnyegner@...nyegner-consulting.de
<mailto:roonnyegner@...nyegner-consulting.de>




Am 21.10.14 09:27 schrieb "NeilBrown" unter <neilb@...e.de>:

>On Tue, 21 Oct 2014 06:33:47 +0000 Ronny Egner
><ronnyegner@...nyegner-consulting.de> wrote:
>
>> Dear All,
>> 
>> i was wondering what happened with the patch posted by Andrea Mazzoleni
>> back in Februrary 2014 (this Thread:
>> http://thread.gmane.org/gmane.linux.kernel/1654735).
>> 
>> Why wash´t it added to the code? Something missing/wrong?
>> 
>> In my opinion the posted patch is awesome and would enable a unique
>> feature that no other UNIX-like operating system currently has.
>> 
>
>Could you report your test results please.
>
>NeilBrown

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