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Unexpectedly small volume size after reluctant factory reset

Bee
Aspirant
Aspirant

Unexpectedly small volume size after reluctant factory reset

Hi,
I have a problem very similar to this one:

http://www.readynas.com/forum/viewtopic.php?f=66&t=75845

I have a Ultra 6 Plus (4.2.27), with 6 disks. It started life with configured as X-RAID2 with (I think) 5x 2TB HDDs, and has gradually been expanded. Recently, I tried to expand from 4x 2794GB and 2x 3726GB by replacing one of the smaller disks with a 5589GB disk. When this expansion failed, I started investigating why, and learned about the 8TB expansion delta limit, and the 16TB expansion ceiling. It occurred to me that I had probably hit the 8TB expansion limit, and the advice I read indicated a reformat and restore should overcome this limit. I decided to get an additional 5589GB disk to get my refreshed array beginning its life above 16TB, so as to avoid hitting the 16TB expansion ceiling (after reading posts like this from Yoh-dah: http://www.readynas.com/forum/viewtopic.php?p=288457&sid=084c6c9a539094ff3ee98bb007c96843#p288047).
And now, after over a month of making, verifying and re-verifying backups and dreading the next step, I took the plunge and reformatted leaving all the disks in place:

3726 GB
5589 GB
2794 GB
5589 GB
2794 GB
3726 GB

I anticipated that this lot should give me a usable space (single disk redundancy) of around 16.5TB

Once the format began (X-RAID2 again), I was surprised to see that it was only giving me a 13TB volume, and that it was specifically resyncing the 6th disk, but I allowed the resync to complete anyway and it told me to restart to expand. Once restarted, I got an error about the expansion failing. So I tried the whole thing again, and got the exact same behaviour. I started wondering if Flex-RAID might behave differently, but so far (it is still doing its first resync) it too is claiming to give me only 13TB. Note that I'd much prefer X-RAID2, anyway.

So, this leaves me with a few questions...
1. Is it expected behaviour for the ReadyNAS to not immediately embrace the whole available capacity?
2. Is this because the disks are a variety of sizes (that is, would it have used all of all of them if they were all the same size)?
3. Is the expansion that it then tries to do failing because it can't cross the 16TB ceiling?
4. Could I fix things by replacing one or more of the smaller disks for larger ones?
5. Alternatively, if I put these same disks in a newer ReadyNAS (running OS6) would I get similar results, or my expected capacity?

Any help would be really appreciated. I can supply logs from before the factory reset as well as after, if needed, or any other info that might help. I really hope I can get this sorted!

Thanks again,
Bee
Message 1 of 5
vandermerwe
Master

Re: Unexpectedly small volume size after reluctant factory r

Should you not be expecting 17.8 TB ?

Have you tested the 6 TB disk?

You are putting all disks in, then factory defaulting the unit?
If it doesn't accept the disks at factory default then it will always fail to expand. The volume need to be setup with all disks at the same time. Remember that you will not be able to expand this volume again without doing another factory default.

Have you considered raid 6 (Xraid with dual redundancy). - I'd strongly recommend it.

You also seem to have a problem backing up, how are you going to maintain regular backups of this volume?

Back it up. Use UPS.
Infrant Readynas NV+ | Readynas Ultra 6 Plus | Readynas 316
Message 2 of 5
StephenB
Guru

Re: Unexpectedly small volume size after reluctant factory r

You can't expand from < 16 TiB to > 16 TiB, and that includes any vertical expansion that happens as part of the initial install. The only way to get > 16 TiB with 4.2.x firmware is to use disks that are all the same size and then do a factory reset. You are using disks of 3 different sizes, so the 16 TiB ceiling still applies. With your particular mix of disks, the system can only use 3 TB capacity from each disk.

That is, your array would need to be constructed as three layers - 6x3TB RAID5 + 4x1TB RAID5 + 2x2TB RAID-1
The first layer would give 15 TB, the second layer adds an additional 3 TB (18 TB total), and the third layer adds 2 TB (20 TB total).

Converting this to TiB gives 13.64 for the first layer, a total of 16.37 for layers 1+2, and 18.18 for all three. Since the first vertical expansion takes you over the 16 TiB ceiling (13.64 TiB -> 16.37 TiB), that expansion fails and the array ends up at 13.6


Installing OS6 on the pro would eliminate that problem, and you'd get the full ~18.2 TB you ought to be seeing.

In my opinion using dual redundancy wouldn't be a great idea, as you'd lose 2 TB of capacity. Backups of course are needed to ensure that your data remains intact.
Message 3 of 5
vandermerwe
Master

Re: Unexpectedly small volume size after reluctant factory r

StephenB wrote:
....and that includes any vertical expansion that happens as part of the initial install.


Ah, never had a volume with different size disks, I had assumed the post factory default volume setup was considered in its entirety for the purposes of volume size.

I agree that OS 6 would provide a good solution.

Back it up. Use UPS.
Infrant Readynas NV+ | Readynas Ultra 6 Plus | Readynas 316
Message 4 of 5
Bee
Aspirant
Aspirant

Re: Unexpectedly small volume size after reluctant factory r

Hi,
Thanks very much for answering my questions.
I have installed OS6 on my RN and it's currently busy building my 18TB volume, so I'm happy! Actually the install was a lot less scary than I expected - things have moved on a great deal since I looked into it last year.
So thanks again!
Bee
Message 5 of 5
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