ReadyNAS PRO 6 / Western Digital Red WD40EFRX

What were the sizes of the disks in your original raid 6 volume, before you added the first two 4tb wd drives?
When you added the subsequent four 4tb drives, did you add them all at the same time or one at a time?

Do you have a backup?

What firmware are you running?

I think the first two drives I replaced were Seagate ST31500341AS units - but it's a long time ago now.

When I started tonight, the config was thus:
Current Disk sizes:
D1: Western Digital WD40EFRX, 1392 Allocated
D2: Western Digital WD40EFRX, 1392 Allocated
D3: Seagate ST31500341AS, 1392 Allocated
D4: Seagate ST2000VN000-1H3164, 1392 Allocated
D5 The dead drive was a Seagate ST31500341AS, 1392 Allocated, now replaced with a Western Digital WD40EFRX (currently syncing)

I stripped D2, D3, D4, D5 and added the new WD40EFRX drives all at once. That left me unable to create a Volume.
I have a backup on my second ReadyNAS Pro 6 :-). Well - I think I do, and the mounts of the backup look OK. I've never recovered it, so it's always possible there's a silent failure.
Firmware is 4.2.27

I'm pondering either 1 by one replacements, or letting the sync finish, taking out all 6 of the current drives, and putting in the other three WD40EFRX drives I have and doing a factory reset/ default FLEXREAID-2 build to see if it works. Both of which are probably dumb ideas, but the best I have at the moment (blush).

Ok.
When you added all four 4 tb disks, did you factory default the nas?
You would of course have lost the data on the volume when you did this.( either just adding them or factory defaulting)
In addition, if you did not factory default, you will have exceed the maximum possible volume expansion of 8TiB when you tried to expand to a raid 6 volume with six 4 tb disks from your original setup which seems to have been mainly 1.5 tb disks with one ( or maybe more ) 2 tb disks. What was the volume size when you last did a factory default.

I would redo your backup and verify it, then backup your config, then factory default the nas with five 4 tb disks in (edited as you won't be able to factory default straight into raid6 of course).Then restore your config. If you have any addons install these before restoring the config. Add the sixth disk and select dual redundancy. Finally restore your data.

This may be useful:
http://ram.kossboss.com/xraid/

I am a little confused on your initial post. But it sounds like you removed 4 disks from a RAID-6 volume, which certainly would kill the original volume.

There are some limits to expansion. One is at 16 TiB total size which shouldn't be a problem. The second is a 8 TiB growth limit, which might be. If you started with 6x1.5 TB RAID-6, then you'd have a 6 TB initial volume, and you are headed for 16 TB. That exceeds the growth limit.

So I think a reset is probably your best bet. Perhaps manually run your backup jobs one last time before you do it. If you are worried, maybe also run a file system check on the backup Pro, and check the SMART stats. Is the backup also RAID-6?

My thanks - and no, I didn't factory default when I added the new drives. So your assessment is undoubtedly correct :-).
The Volume size now is exactly what it was when I first configured it - so yes, I easily exceeded the max growth, which I can either claim I forgot because I'm old enough to be a National Monument, or never remembered, because I haven;t played with the unit in ages. My thanks indeed, Sir! I'll let the backup run again tonight, then try a reset tomorrow. And yes, the backup unit is RAID 6 as well. It's smaller than the main unit, but big enough for the parts of the main unit I actually need to restore.
Any comments on a new RAID 6, or putting it in as FLEX? My thought is that as far as I know the 4TB drives are as big as the Pro can handle, so I'm not likely to be trying to increase size again, so stick with RAID 6.
Thank you again, sir :-)).

I'd stick with raid 6.
The pro 6 isn't limited to 4 tb disks, although there are no 6 tb disks on the compatibility list (yet)

Even if you had not exceeded the limit, you would not have been successful at adding 4 new disks at the same time while preserving the volume. With raid six the maximum number of disks you could remove and replace at one time would be two, however this would not be a good idea as your volume is then not redundant and the resync could lead to a failure of 1 of the remaining disks, which would lead to loss of the volume. One disk at a time, allowing resync to complete before adding the next is the way to do it if you want to preserve the existing volume.

As we've suggested, make sure your backup is perfect, then factory default. Remember to backup the config first.

with 6x4TB there isn't really much difference between flexraid RAID-6 and XRAID dual redundancy. The volume won't be expandable either way. I'd probably stick with XRAID. Start with 5 disks installed, and let it initialize with single redundancy. Then check the box for "adding for redundancy" and hot-insert the final drive.

If you choose to save/restore your current configuration file, then make sure you install any add-ons you are using before you do the restore.

vandermerwe wrote:
Even if you had not exceeded the limit, you would not have been successful at adding 4 new disks at the same time while preserving the volume. With raid six the maximum number of disks you could remove and replace at one time would be two,

Aye - that bit was just me being dumb. I thought (old memory) that if the NAS didn't see a 'good' volume, it defaulted into setup mode. If I'd remembered I had to do a factory reset, I wouldn't have had to waste your time reminding me things I should have remembered :-).

No worries.
I edited one of my previous posts in response to StephenB's post which reminded me that you won't be able to factory default straight into raid 6, so you'll need to do it ( factory default) with 5 disks, then add the 6th after the volume has been set up.

My thanks to both of you, sirs :-)).