Quick question about expanding a volume with a ReadyNAS Pro 6

Dear Community, I have A Ready NAS Pro 6 3x1TB It is runnign verison 4.2.30 Wondering if I could expand and create the best redundancy as possible. I was thinking 3x4 WD Red drives - Enter...

Adding Disks

ReadyNAS OS 6 on Legacy models

StephenB
Apr 17, 2017
peteophoven wrote:

I believe I cannot expand the current volume over 8 TB right?

There are two expansion limits with XRAID:

a volume cannot grow more than 8 TiB over it's lifetime

a volume can expand over a 16 TiB ceiling

The first limit applies here.

If you initially installed 3x1TB, then you can grow your volume to about 10 TB.

If you initially installed 1TB, and then added the other two, then you can grow your volume to about 9 TB.

If you have a 9 TB ceiling, then you can replace two of your 1 TB drives (one at a time) with 4TB models, and install the third 4 TB drive in an empty slot. You'll end up with a 9 TB volume.

If you have a 10 TB ceiling, then replace one of the 1 TB drives, and install two 4 TB drives in empty slots. You'll end up with a 10 TB volume.

Once you hit the expansion limit you need to do a factory reset to expand further. That will destroy your data, so you will need to restore it from a backup.

peteophoven wrote:

... but want to be smart about adding the drives to allow for maximum redundancy, so if two drives fail I will still be okay,

You have single redundancy now. If you want dual redundancy, then you need to have four drives of the largest size - not three.

You'd follow the guidance above to expand the volume. There is a checkbox that let's you choose to add the final drive for redundancy. You'd check that box, and install the fourth 4TB drive in an empty slot.

peteophoven wrote:

...I was thinking 3x4 WD Red drives - Enterprise.

WD Reds are good drives (I use them in my own ReadyNAS). They are NAS-purposed, acoustically quiet, run cool, and have 3 year warranties. But they are not enterprise drives.

WD Red Pros are the enterprise models. They run at 7200 rpm, so they use more power and your NAS will have higher temps. Performance will be better in some cases (in others your network limits your performance, not the drives). They have 5 year warranties.

peteophoven

Aspirant

Apr 17, 2017

This is a great response. Very comprehensive.
I see the advantage of a factory reset but I really have little room to be out of production.
I think adding 3x4tb drives, staged, one at a time will do the trick.
The the third for redundancy.
We started with 3x1tb giving us 1.8 as the volume size.
Will I lose capacity due to parity when adding the 4tb drives?
When I add the the third drive and indicate redundancy - will the resync cause my volume to be offline?
Thank you.

mdgm-ntgr
NETGEAR Employee Retired
Apr 18, 2017
With 3x4TB disks you'd expect roughly 4x the volume capacity you have now.
StephenB
Guru - Experienced User
Apr 18, 2017
peteophoven wrote:

We started with 3x1tb giving us 1.8 as the volume size.
Will I lose capacity due to parity when adding the 4tb drives?

If you go back to my earler post, you'll see I covered this case.

Your volume can grow to 9.8 TiB (~10.8 TB), but no more. If you simply add the three 4 TB drives (leaving the 3x1 TB in place) then you would have an 11 TB volume - just over the limit. When you try to add the last drive the expansion will fail.

That is why I said you'd need to replace one of the 1 TB drives with a 4 TB drive. Then you'd end up with 2x1TB+3x4TB, with a volume size of ~9.1 TiB (10 TB).

The general capacity rule for XRAID single redundancy is "sum the drives and subtract the largest". In your scenario you need 4 TB of parity blocks. Anything less can't recover from a failed 4 TB drive. With dual redundancy, you need an additional 4 TB of parity blocks (computed differently) - anything less can't recover from two failed 4 TB drives. These parity blocks are evenly distributed across all the drives.

peteophoven wrote:

When I add the the third drive and indicate redundancy

That's NOT the process if you are adding 3x4TB.

Here are the steps:

remove one 1TB drive with the system running

hot-insert the first 4 TB drive into that slot. Wait for resync to complete. Final volume size will be 1.8TiB.

hot-insert the second 4 TB drive into an empy slot. Wait for resync to complete. Final volume size will be 4.5 TiB You might need to reboot in the middle of the resync to get that expansion (the system should prompt for that).

hot-insert the third 4 TB drive into an empty slot. Wait for resync to complete. Final volume size will be 9.1 TiB

If you want dual-redundancy (protection from two drive failures), you add these steps at the end

indicate that you want to add a disk for redundancy

hot-insert a fourth 4 TB drive into an empty slot. Wait for resync to complete. Final volume size will still be 9.1 TiB (with 8 TB of parity blocks).

peteophoven wrote:

will the resync cause my volume to be offline?

No. The system is available during resyncs, but at a reduced performance level. Resync times will go up as you add more disks, and will take quite a bit longer if you add the 4th 4 TB drive (since it doubles the number of parity blocks that need to be computed).

During the first series of steps, the volume is not protected from failure while a resync is in process. So it is particularly important to have current backups during those steps. If you go with dual redundancy, the volume is protected from single-disk failure during the resync with the final 4 TB drive.

Replacing the 1 TB drive with the 4 TB drive will resync pretty quickly, so doing it off-hours during the work week will probably be ok. After that, I'd suggest doing the hot-insertions on the weekends. Note you will probably will need to reboot when the second 4 TB is inserted (part-way through the resync).
Sandshark
Sensei
Apr 18, 2017
peteophoven wrote:
This is a great response. Very comprehensive.
I see the advantage of a factory reset but I really have little room to be out of production.
I can see that being an issue if you don't have enough down time (like a weekend) in which to perform it. It's just that with under 1.8TB of data, it's a lot easier to restore all that now than if you find you need to expand again after you've filled your max volume expansion. Moving to OS 6.0 lifts that limit, too. You are completely down with a factory reset and restore, even if you don't go to OS 6.x, while you are not during an expansion only.