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btrfs - remove drive from raid array

in flag
Nathan

I have 4 (3TB) drives used for backups inside my PC case I want to migrate to a NAS bay. I was wondering if the drives could be migrated over one at a time by disabling RAID. Here is the output from btrfs filesystem usage:

Overall:
Device size:          10.92TiB
Device allocated:          8.44TiB
Device unallocated:        2.47TiB
Device missing:          0.00B
Used:              8.43TiB
Free (estimated):          1.24TiB  (min: 1.24TiB)
Free (statfs, df):         1.24TiB
Data ratio:               2.00
Metadata ratio:           2.00
Global reserve:      512.00MiB  (used: 0.00B)
Multiple profiles:              no

Data,RAID6: Size:4.21TiB, Used:4.21TiB (99.84%)
/dev/mapper/sdb_crypt      2.11TiB
/dev/mapper/sdc_crypt      2.11TiB
/dev/mapper/sdd_crypt      2.11TiB
/dev/mapper/sde_crypt      2.11TiB

Metadata,RAID6: Size:6.00GiB, Used:5.33GiB (88.87%)
/dev/mapper/sdb_crypt      3.00GiB
/dev/mapper/sdc_crypt      3.00GiB
/dev/mapper/sdd_crypt      3.00GiB
/dev/mapper/sde_crypt      3.00GiB

System,RAID6: Size:64.00MiB, Used:448.00KiB (0.68%)
/dev/mapper/sdb_crypt     32.00MiB
/dev/mapper/sdc_crypt     32.00MiB
/dev/mapper/sdd_crypt     32.00MiB
/dev/mapper/sde_crypt     32.00MiB

Unallocated:
/dev/mapper/sdb_crypt    633.49GiB
/dev/mapper/sdc_crypt    633.49GiB
/dev/mapper/sdd_crypt    633.49GiB
/dev/mapper/sde_crypt    633.49GiB

Can anyone advise on how to tackle this? I would like to know if it's possible to move the drives over. Obviously, this is easily solved with buying more drives to fill out the NAS bay, but this is a homelab setup, so I'm doing things on the cheap. :)

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paladin avatar
id flag
paladin
You should not use btrfs raid 5 or 6 as those are experimental. Data lose is imminent, do a full backup and switch to btrfs raid1 or btrfs raid10.
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Nathan
@paladin agreed. That is why I bought the NAS. I don’t have a backup drive big enough. What drive size do you recommend?
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paladin avatar
id flag
paladin
Dual 18TByte raid1, easy to manage, solid and safe for future. WesternDigital drives may be a bit slower than Seagate, but they also become less hot and are less noisy. I would use btrfs raid1. If you can afford, buy SAS (SCSI) drives instead of SATA. Use also SSD as system disk (WD Blue have long life time.).
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djdomi avatar Server
za flag
djdomi

Raid

RAID 6 requires a minimum of 4 drives.

Reference:

My own Knowledge
Wikipedia

So the Answer will be:

No, you will not be able to do so.

It will break the raid system and the data will be gone.

Solving:

create a Backup, move the Drives and Re-Create it. Mostly any Consumer NAS will only accept, that you need and forced to re-create the full RAID. Thereforce all data will be DELETED and well... gone forever... :)

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