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Solved
Problem Adding a Drive to ReadyNAS RN628X
I've had a ReadyNAS RN628X for a few years. The first 4 drives were 12 TB and I expanded with 2 16TB drives. The size of the volume expanded as expected each time. It was around 58 TB with 6 drives...
OK, so this is the command you need to issue from SSH to change it to RAID5:
mdadm --grow /dev/md127 --level=5 --raid-devices=7 --force --verbose
That will cause it to re-sync to a RAID5 configuration. For some reason, you may need to issue it again once the sync is complete for it to be properly recognized as RAID5, but it won't have to re-sync again. If you add yet another drive, you'll have to do it again (with --raid-devices=8, obviously) and you'll likely need to do it for md126, too (with 4 devices), as it will convert to RAID6 when the 4th drive is added (at least that's what happens on my 12-bay NAS).
As with any sync, a power cycle can be deadly to your volume and things can always go wrong. So insure your backup is up to date and your NAS is on an UPS before you do this.
If that doesn't work, as it didn't once for me, you will have to convert to FlexRAID and remove one drive (logically, not physically) from the volume and re-install it.
For reference, see here:RAID6-to-RAID5-without-volume-re-creation-is-possible
Actually, it turns out it isn't normally necessary to disable XRAID to use SSH to convert from RAID6 to RAID5. I don't know why I had to one time I did it, but I've done it since and didn't need to. Every time I upgrade a drive in my XRAID/RAID5 12-bay NAS, the RAID group that expands is made into RAID6 instead of RAID5, so I have to switch it. This seems to be a bug in the OS, making the second RAID group RAID6 once more than 4 drives are in it even though the first group is RAID5.
If you post the results of the cat /proc/mdstat command, I can give you the specific command necessary to do it.
I thought I posted a reply, but it doesn't look like it went through.
I did once know about the RAID 5 parity vs stripe drive thing, but had a brain fart. And I was imprecise about my language on the size. I was pretty tired yesterday and I don't work with this stuff everyday...
The issue with the RaidX converting the array to a RAID 6 explains everything. I don't think we need the double protection from RAID 6, so converting it back to RAID 5 is probably a better solution.
Here is the result of the cat /pro/mdstat/ command
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md126 : active raid5 sde4[0] sdg4[2] sdf4[1]
7813728128 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
md127 : active raid6 sda3[0] sdg3[6] sdf3[5] sde3[4] sdd3[3] sdc3[2] sdb3[1]
58570168000 blocks super 1.2 level 6, 64k chunk, algorithm 2 [7/7] [UUUUUU U]
md1 : active raid10 sda2[0] sdg2[6] sdf2[5] sde2[4] sdd2[3] sdc2[2] sdb2[1]
1827840 blocks super 1.2 512K chunks 2 near-copies [7/7] [UUUUUUU]
md0 : active raid1 sda1[0] sdg1[6] sdf1[5] sde1[4] sdd1[3] sdc1[2] sdb1[1]
4190208 blocks super 1.2 [7/7] [UUUUUUU]
I assume the RAID 10 and RAID 1 are something the OS uses? They look small.
wdolson wrote:
md126 : active raid5 sde4[0] sdg4[2] sdf4[1]
7813728128 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU]md127 : active raid6 sda3[0] sdg3[6] sdf3[5] sde3[4] sdd3[3] sdc3[2] sdb3[1]
58570168000 blocks super 1.2 level 6, 64k chunk, algorithm 2 [7/7] [UUUUUU U]Yes, md127 (the 7 drive RAID group) is RAID-6, and md126 (the 3 driver RAID group) is RAID-5. So this confirms what I was thinking.
wdolson wrote:
I assume the RAID 10 and RAID 1 are something the OS uses? They look small.
md0 is the 4 GB OS partition (the NAS boots from this, so it is mirrored on every drive).
md1 is the swap partition.
Thanks for getting my post out of the spam filter jail.
It's always a good feeling when the data lines up with the theory.
OK, so this is the command you need to issue from SSH to change it to RAID5:
mdadm --grow /dev/md127 --level=5 --raid-devices=7 --force --verbose
That will cause it to re-sync to a RAID5 configuration. For some reason, you may need to issue it again once the sync is complete for it to be properly recognized as RAID5, but it won't have to re-sync again. If you add yet another drive, you'll have to do it again (with --raid-devices=8, obviously) and you'll likely need to do it for md126, too (with 4 devices), as it will convert to RAID6 when the 4th drive is added (at least that's what happens on my 12-bay NAS).
As with any sync, a power cycle can be deadly to your volume and things can always go wrong. So insure your backup is up to date and your NAS is on an UPS before you do this.
If that doesn't work, as it didn't once for me, you will have to convert to FlexRAID and remove one drive (logically, not physically) from the volume and re-install it.
For reference, see here:RAID6-to-RAID5-without-volume-re-creation-is-possible
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