Hi
Well, I think it is worth to give more details on the array.
the array is built with 5x8TB HDD in an esternal USB3.0 to SATAIII enclosure
The enclosure is a cheap JMicron based chinese stuff (from Orico).
There is one USB3.0 link for all the 5 HDD with a SATAIII 3.0Gb
multiplexer behind it. So you cannot expect peak performance, which is
not the goal of this array (domestic data storage).
Also the USB to SATA firmware is buggy, so UAS operations are not
stable, it run in BOT mode.
Having said so, the scrub has been started (and resumed) on the array
mount point:
sudo btrfs scrub start(resume) /media/storage/das1
even if reading the documentation I understand that it is the same
invoking it on mountpoint or one of the HDD in the array.
In the end, especially for a RAID5 array, does it really make sense to
scrub only one disk in the array???
Regarding the data usage, here you have the current figures:
menion@Menionubuntu:~$ sudo btrfs fi show
[sudo] password for menion:
Label: none uuid: 6db4baf7-fda8-41ac-a6ad-1ca7b083430f
Total devices 1 FS bytes used 11.44GiB
devid 1 size 27.07GiB used 18.07GiB path /dev/mmcblk0p3
Label: none uuid: 931d40c6-7cd7-46f3-a4bf-61f3a53844bc
Total devices 5 FS bytes used 6.57TiB
devid 1 size 7.28TiB used 1.64TiB path /dev/sda
devid 2 size 7.28TiB used 1.64TiB path /dev/sdb
devid 3 size 7.28TiB used 1.64TiB path /dev/sdc
devid 4 size 7.28TiB used 1.64TiB path /dev/sdd
devid 5 size 7.28TiB used 1.64TiB path /dev/sde
menion@Menionubuntu:~$ sudo btrfs fi df /media/storage/das1
Data, RAID5: total=6.57TiB, used=6.56TiB
System, RAID5: total=12.75MiB, used=416.00KiB
Metadata, RAID5: total=9.00GiB, used=8.16GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
menion@Menionubuntu:~$ sudo btrfs fi usage /media/storage/das1
WARNING: RAID56 detected, not implemented
WARNING: RAID56 detected, not implemented
WARNING: RAID56 detected, not implemented
Overall:
Device size: 36.39TiB
Device allocated: 0.00B
Device unallocated: 36.39TiB
Device missing: 0.00B
Used: 0.00B
Free (estimated): 0.00B (min: 8.00EiB)
Data ratio: 0.00
Metadata ratio: 0.00
Global reserve: 512.00MiB (used: 32.00KiB)
Data,RAID5: Size:6.57TiB, Used:6.56TiB
/dev/sda 1.64TiB
/dev/sdb 1.64TiB
/dev/sdc 1.64TiB
/dev/sdd 1.64TiB
/dev/sde 1.64TiB
Metadata,RAID5: Size:9.00GiB, Used:8.16GiB
/dev/sda 2.25GiB
/dev/sdb 2.25GiB
/dev/sdc 2.25GiB
/dev/sdd 2.25GiB
/dev/sde 2.25GiB
System,RAID5: Size:12.75MiB, Used:416.00KiB
/dev/sda 3.19MiB
/dev/sdb 3.19MiB
/dev/sdc 3.19MiB
/dev/sdd 3.19MiB
/dev/sde 3.19MiB
Unallocated:
/dev/sda 5.63TiB
/dev/sdb 5.63TiB
/dev/sdc 5.63TiB
/dev/sdd 5.63TiB
/dev/sde 5.63TiB
menion@Menionubuntu:~$
menion@Menionubuntu:~$ sf -h
The program 'sf' is currently not installed. You can install it by typing:
sudo apt install ruby-sprite-factory
menion@Menionubuntu:~$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 934M 0 934M 0% /dev
tmpfs 193M 22M 171M 12% /run
/dev/mmcblk0p3 28G 12G 15G 44% /
tmpfs 962M 0 962M 0% /dev/shm
tmpfs 5,0M 0 5,0M 0% /run/lock
tmpfs 962M 0 962M 0% /sys/fs/cgroup
/dev/mmcblk0p1 188M 3,4M 184M 2% /boot/efi
/dev/mmcblk0p3 28G 12G 15G 44% /home
/dev/sda 37T 6,6T 29T 19% /media/storage/das1
tmpfs 193M 0 193M 0% /run/user/1000
menion@Menionubuntu:~$ btrfs --version
btrfs-progs v4.17
So I don't fully understand where the scrub data size comes from
Il giorno lun 13 ago 2018 alle ore 23:56 <erentheti...@mail.de> ha scritto:
>
> Running time of 55:06:35 indicates that the counter is right, it is not
> enough time to scrub the entire array using hdd.
>
> 2TiB might be right if you only scrubbed one disc, "sudo btrfs scrub start
> /dev/sdx1" only scrubs the selected partition,
> whereas "sudo btrfs scrub start /media/storage/das1" scrubs the actual array.
>
> Use "sudo btrfs scrub status -d " to view per disc scrubbing statistics and
> post the output.
> For live statistics, use "sudo watch -n 1".
>
> By the way:
> 0 errors despite multiple unclean shutdowns? I assumed that the write hole
> would corrupt parity the first time around, was i wrong?
>
> Am 13-Aug-2018 09:20:36 +0200 schrieb men...@gmail.com:
> > Hi
> > I have a BTRFS RAID5 array built on 5x8TB HDD filled with, well :),
> > there are contradicting opinions by the, well, "several" ways to check
> > the used space on a BTRFS RAID5 array, but I should be aroud 8TB of
> > data.
> > This array is running on kernel 4.17.3 and it definitely experienced
> > power loss while data was being written.
> > I can say that it wen through at least a dozen of unclear shutdown
> > So following this thread I started my first scrub on the array. and
> > this is the outcome (after having resumed it 4 times, two after a
> > power loss...):
> >
> > menion@Menionubuntu:~$ sudo btrfs scrub status /media/storage/das1/
> > scrub status for 931d40c6-7cd7-46f3-a4bf-61f3a53844bc
> > scrub resumed at Sun Aug 12 18:43:31 2018 and finished after 55:06:35
> > total bytes scrubbed: 2.59TiB with 0 errors
> >
> > So, there are 0 errors, but I don't understand why it says 2.59TiB of
> > scrubbed data. Is it possible that also this values is crap, as the
> > non zero counters for RAID5 array?
> > Il giorno sab 11 ago 2018 alle ore 17:29 Zygo Blaxell
> > <ce3g8...@umail.furryterror.org> ha scritto:
> > >
> > > On Sat, Aug 11, 2018 at 08:27:04AM +0200, erentheti...@mail.de wrote:
> > > > I guess that covers most topics, two last questions:
> > > >
> > > > Will the write hole behave differently on Raid 6 compared to Raid 5 ?
> > >
> > > Not really. It changes the probability distribution (you get an extra
> > > chance to recover using a parity block in some cases), but there are
> > > still cases where data gets lost that didn't need to be.
> > >
> > > > Is there any benefit of running Raid 5 Metadata compared to Raid 1 ?
> > >
> > > There may be benefits of raid5 metadata, but they are small compared to
> > > the risks.
> > >
> > > In some configurations it may not be possible to allocate the last
> > > gigabyte of space. raid1 will allocate 1GB chunks from 2 disks at a
> > > time while raid5 will allocate 1GB chunks from N disks at a time, and if
> > > N is an odd number there could be one chunk left over in the array that
> > > is unusable. Most users will find this irrelevant because a large disk
> > > array that is filled to the last GB will become quite slow due to long
> > > free space search and seek times--you really want to keep usage below 95%,
> > > maybe 98% at most, and that means the last GB will never be needed.
> > >
> > > Reading raid5 metadata could theoretically be faster than raid1, but that
> > > depends on a lot of variables, so you can't assume it as a rule of thumb.
> > >
> > > Raid6 metadata is more interesting because it's the only currently
> > > supported way to get 2-disk failure tolerance in btrfs. Unfortunately
> > > that benefit is rather limited due to the write hole bug.
> > >
> > > There are patches floating around that implement multi-disk raid1 (i.e. 3
> > > or 4 mirror copies instead of just 2). This would be much better for
> > > metadata than raid6--more flexible, more robust, and my guess is that
> > > it will be faster as well (no need for RMW updates or journal seeks).
> > >
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