Finally have btrfs setup in RAID1

EricMesa

March 21, 2017 - 3 minutes read - 443 words

A little under 3 years ago, I started exploring btrfs for its ability to help me limit data loss. Since then I’ve implemented a snapshot script to take advantage of the Copy-on-Write features of btrfs. But I hadn’t yet had the funds and the PC case space to do RAID1. I finally was able to implement it for my photography hard drive. This means that, together with regular scrubs, I should have a near miniscule chance of bit rot ruining any photos it hasn’t already corrupted.

Here’s a documentation of some commands and how I got the drives into RAID1:

Before RAID:

# btrfs fi df -h /media/Photos
Data, single: total=2.31TiB, used=2.31TiB
System, DUP: total=8.00MiB, used=272.00KiB
System, single: total=4.00MiB, used=0.00B
Metadata, DUP: total=3.50GiB, used=2.68GiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=512.00MiB, used=0.00B

# btrfs fi usage /media/Photos
Overall:
    Device size:                   2.73TiB
    Device allocated:              2.32TiB
    Device unallocated:          423.48GiB
    Device missing:                  0.00B
    Used:                          2.31TiB
    Free (estimated):            425.29GiB      (min: 213.55GiB)
    Data ratio:                       1.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 5.64MiB)

Data,single: Size:2.31TiB, Used:2.31TiB
   /dev/sdd1       2.31TiB

Metadata,single: Size:8.00MiB, Used:0.00B
   /dev/sdd1       8.00MiB

Metadata,DUP: Size:3.50GiB, Used:2.68GiB
   /dev/sdd1       7.00GiB

System,single: Size:4.00MiB, Used:0.00B
   /dev/sdd1       4.00MiB

System,DUP: Size:8.00MiB, Used:272.00KiB
   /dev/sdd1      16.00MiB

Unallocated:
   /dev/sdd1     423.48GiB

[root@supermario ~]# btrfs device add /dev/sda1 /media/Photos/
/dev/sda1 appears to contain an existing filesystem (btrfs).
ERROR: use the -f option to force overwrite of /dev/sda1
[root@supermario ~]# btrfs device add /dev/sda1 /media/Photos/ -f

[root@supermario ~]# btrfs fi usage /media/Photos
Overall:
    Device size:                   6.37TiB
    Device allocated:              2.32TiB
    Device unallocated:            4.05TiB
    Device missing:                  0.00B
    Used:                          2.31TiB
    Free (estimated):              4.05TiB      (min: 2.03TiB)
    Data ratio:                       1.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 0.00B)

Data,single: Size:2.31TiB, Used:2.31TiB
   /dev/sdd1       2.31TiB

Metadata,single: Size:8.00MiB, Used:0.00B
   /dev/sdd1       8.00MiB

Metadata,DUP: Size:3.50GiB, Used:2.68GiB
   /dev/sdd1       7.00GiB

System,single: Size:4.00MiB, Used:0.00B
   /dev/sdd1       4.00MiB

System,DUP: Size:8.00MiB, Used:272.00KiB
   /dev/sdd1      16.00MiB

Unallocated:
   /dev/sda1       3.64TiB
   /dev/sdd1     423.48GiB

[root@supermario ~]# btrfs balance start -dconvert=raid1 -mconvert=raid1 /media/Photos/

Done, had to relocate 2374 out of 2374 chunks

Post-RAID:

[root@supermario ~]# btrfs fi usage /media/Photos
Overall:
    Device size:                   6.37TiB
    Device allocated:              4.63TiB
    Device unallocated:            1.73TiB
    Device missing:                  0.00B
    Used:                          4.62TiB
    Free (estimated):            891.01GiB      (min: 891.01GiB)
    Data ratio:                       2.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 0.00B)

Data,RAID1: Size:2.31TiB, Used:2.31TiB
   /dev/sda1       2.31TiB
   /dev/sdd1       2.31TiB

Metadata,RAID1: Size:7.00GiB, Used:2.56GiB
   /dev/sda1       7.00GiB
   /dev/sdd1       7.00GiB

System,RAID1: Size:64.00MiB, Used:368.00KiB
   /dev/sda1      64.00MiB
   /dev/sdd1      64.00MiB

Unallocated:
   /dev/sda1       1.32TiB
   /dev/sdd1     422.46GiB

[root@supermario ~]# btrfs fi df -h /media/Photos
Data, RAID1: total=2.31TiB, used=2.31TiB
System, RAID1: total=64.00MiB, used=368.00KiB
Metadata, RAID1: total=7.00GiB, used=2.56GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

And here’s the status of my first scub to test out the commands:

[root@supermario ~]# btrfs scrub status /media/Photos/
scrub status for 27cc1330-c4e3-404f-98f6-f23becec76b5
 scrub started at Tue Mar 21 17:18:13 2017, running for 00:09:10
 total bytes scrubbed: 145.57GiB with 0 errors

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