On Wednesday, 18 March 2020 21:11:56 UTC Goffredo Baroncelli wrote:
> Hi all,
>
> this patch adds support for the raid5/6 profiles in the command
> 'btrfs filesystem usage'.
>
> Until now the problem was that the value r_{data,metadata}_used is not
> easy to get for a RAID5/6, because it depends by the number of disks.
> And in a filesystem it is possible to have several raid5/6 chunks with a
> different number of disks.
>
> In order to bypass this issue, I reworked the code to get rid of these
> values where possible and to use the l_{data,metadata}_used ones.
> Notably the biggest differences is in how the free space estimation
> is computed. Before it was:
>
> free_estimated = (r_data_chunks - r_data_used) / data_ratio;
>
> After it is:
>
> free_estimated = l_data_chunks - l_data_used;
>
> which give the same results when there is no mixed raid level, but a
> better result in the other case. I have to point out that before in the
> code there was a comment that said the opposite.
>
> The other place where the r_{data,metadata}_used are use is for the
> "Used:" field. For this case I estimated these values using the
> following formula (only for raid5/6 profiles):
>
> r_data_used += (double)r_data_chunks * l_data_used /
> l_data_chunks;
>
> Note that this is not fully accurate. Eg. suppose to have two raid5 chunks,
> the first one with 3 disks, the second one with 4 disks, and that each
> chunk is 1GB.
> r_data_chunks_r56, l_data_used_r56, l_data_chunks_r56 are completely
> defined, but real r_data_used is completely different in these two cases:
> - the first chunk is full and the second one id empty
> - the first chunk is full empty and the second one is full
> However now this error affect only the "Used:" field.
>
>
> So now if you run btrfs fi us in a raid6 filesystem you get:
>
> $ sudo btrfs fi us /
> Overall:
> Device size: 40.00GiB
> Device allocated: 8.28GiB
> Device unallocated: 31.72GiB
> Device missing: 0.00B
> Used: 5.00GiB
> Free (estimated): 17.36GiB (min: 17.36GiB)
> Data ratio: 2.00
> Metadata ratio: 0.00
> Global reserve: 3.25MiB (used: 0.00B)
>
> Data,RAID6: Size:4.00GiB, Used:2.50GiB (62.53%)
> [...]
>
> Instead before:
>
> $ sudo btrfs fi us /
> WARNING: RAID56 detected, not implemented
> WARNING: RAID56 detected, not implemented
> WARNING: RAID56 detected, not implemented
> Overall:
> Device size: 40.00GiB
> Device allocated: 0.00B
> Device unallocated: 40.00GiB
> Device missing: 0.00B
> Used: 0.00B
> Free (estimated): 0.00B (min: 8.00EiB)
> Data ratio: 0.00
> Metadata ratio: 0.00
> Global reserve: 3.25MiB (used: 0.00B)
>
> Data,RAID6: Size:4.00GiB, Used:2.50GiB (62.53%)
> [...]
>
>
> I want to point out that this patch should be compatible with my
> previous patches set (the ones related to the new ioctl
> BTRFS_IOC_GET_CHUNK_INFO). If both are merged we will have a 'btrfs fi us'
> commands with full support a raid5/6 filesystem without needing root
> capability.
>
> Comments are welcome.
> BR
> G.Baroncelli
Hi Goffredo
Thanks you for this. It's something I've been wanting for a while. Do
you know why I get significantly different results in the overall summary when I
do not run it as root. I'm not sure if this is a bug or a limitation.
When I run it as root it looks to be showing the correct values.
joshua@r2400g:~/development/btrfs-progs$ colordiff -u <(./btrfs fi us /mnt/raid/) <(sudo ./btrfs fi us /mnt/raid/)
WARNING: cannot read detailed chunk info, per-device usage will not be shown, run as root
--- /dev/fd/63 2020-04-13 10:54:26.833747190 +0100
+++ /dev/fd/62 2020-04-13 10:54:26.843746984 +0100
@@ -1,17 +1,32 @@
Overall:
Device size: 29.11TiB
- Device allocated: 284.06GiB
- Device unallocated: 28.83TiB
- Device missing: 29.11TiB
- Used: 280.99GiB
- Free (estimated): 0.00B (min: 14.95TiB)
- Data ratio: 0.00
+ Device allocated: 19.39TiB
+ Device unallocated: 9.72TiB
+ Device missing: 0.00B
+ Used: 18.67TiB
+ Free (estimated): 7.82TiB (min: 5.39TiB)
+ Data ratio: 1.33
Metadata ratio: 2.00
Global reserve: 512.00MiB (used: 0.00B)
Data,RAID5: Size:14.33TiB, Used:13.80TiB (96.27%)
+ /dev/mapper/traid3 4.78TiB
+ /dev/mapper/traid1 4.78TiB
+ /dev/mapper/traid2 4.78TiB
+ /dev/mapper/traid4 4.78TiB
Metadata,RAID1: Size:142.00GiB, Used:140.49GiB (98.94%)
+ /dev/mapper/traid3 63.00GiB
+ /dev/mapper/traid1 64.00GiB
+ /dev/mapper/traid2 63.00GiB
+ /dev/mapper/traid4 94.00GiB
System,RAID1: Size:32.00MiB, Used:1.00MiB (3.12%)
+ /dev/mapper/traid1 32.00MiB
+ /dev/mapper/traid4 32.00MiB
+Unallocated:
+ /dev/mapper/traid3 2.44TiB
+ /dev/mapper/traid1 2.44TiB
+ /dev/mapper/traid2 2.44TiB
+ /dev/mapper/traid4 2.41TiB
This is in contrast to raid1 which seems to be mostly correct, irrespective
of what user I run as.
joshua@arch:/var/joshua$ colordiff -u <(btrfs fi us raid/) <(sudo btrfs fi us raid/)
WARNING: cannot read detailed chunk info, per-device usage will not be shown, run as root
--- /dev/fd/63 2020-04-13 09:52:54.630750079 +0000
+++ /dev/fd/62 2020-04-13 09:52:54.637416835 +0000
@@ -2,7 +2,7 @@
Device size: 8.00GiB
Device allocated: 1.32GiB
Device unallocated: 6.68GiB
- Device missing: 8.00GiB
+ Device missing: 0.00B
Used: 383.40MiB
Free (estimated): 3.55GiB (min: 3.55GiB)
Data ratio: 2.00
@@ -10,8 +10,17 @@
Global reserve: 3.25MiB (used: 0.00B)
Data,RAID1: Size:409.56MiB, Used:191.28MiB (46.70%)
+ /dev/loop0 409.56MiB
+ /dev/loop1 409.56MiB
Metadata,RAID1: Size:256.00MiB, Used:416.00KiB (0.16%)
+ /dev/loop0 256.00MiB
+ /dev/loop1 256.00MiB
System,RAID1: Size:8.00MiB, Used:16.00KiB (0.20%)
+ /dev/loop0 8.00MiB
+ /dev/loop1 8.00MiB
+Unallocated:
+ /dev/loop0 3.34GiB
+ /dev/loop1 3.34GiB
Does anyone know if this is something we can fix? I'm happy to take a look.
Joshua Houghton
