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mdadm RAID Upgrade Advice

Posted: 2021/01/04 01:13:15
by mphelpsmd
I'm running CentOS 8.3 and I'm currently using mdadm for software RAID.

I have an 8-bay external SAS enclosure, of which 5 are currently used (4 TB apiece) as a RAID6 array with 12 TB of usable storage. The other 3 bays have local backup drives that get rotated in and out of the system.

When it comes time to upgrade to an enlarged RAID array, I have a couple options:

1) Remove one of the backup drives and insert a new 8TB hard drive into that slot, replace one of the RAID drives with the new drive, remove the RAID drive and continue this until all RAID drives are upgraded to 8 TB drives. Then grow the array to the maximum size (24 TB of usable space in RAID6 with 5 HDD's).

2) Fail and remove one of the RAID drives to operate in a degraded RAID6. Then use the remaining 4 bays to make a new RAID6 array of 12 TB HDD's. Rsync the old RAID array to the new one and remove the old array. This results in 24 TB of usable space in RAID6 with 4 HDD's.

I'm leaning towards options #2 because it would leave me with an extra bay, and I anticipate the time coming where I will need two drives in RAID0, rather than just a single drive, for backups.

Does anyone have any thoughts on this, or a better solution? I can tolerate a few days of downtime to make the copy, so 24/7 uptime isn't critical here for my home server.