ReadyNAS Ultra 4 with 4TB

You need a second 4TB disk installed to be able to use additional space. X-RAID2 volumes can only be expanded when redundant space can be added.

Please also note a couple of expansion limits:

1. You cannot expand by more than 8TB over the life of the volume. If the volume capacity was 1.8TB when you last did a factory default (wipes all data, settings, everything) you cannot expand past 9.8TB
2. You cannot expand past 16TB. To have a volume capacity >16TB you would need to do a factory default (wipes all data, settings, everything) with the drives in place.

Thanks for the help. So, I'm not sure if your (1.) means I can or cannot add another 4TB in slot 4. That would bring me to 12TB total. When I bought the unit, it was built with 2x2TB and I haven't done a factory default since.

It sounds like I could add 4TB, then swap out the 2 2TB drives and replace them with 2 4TB drives? I'd rather just add another 4TB drive if that's doable.

Adding the second 4TB drive to the empty slot you would not hit the 8TB limit. Your volume would expand by around 3.7TB. 1.8TB (from adding first 4TB disk) + 3.7TB (after adding second) < 8TB, however when you need even more space then a backup and factory reset will become necessary.

The key idea here is that the 8 TiB limit applies to the volume size, not the raw disk sizes. You will end up with an ~8TB volume, so you can't exceed the 8 TiB growth limit no matter where you started from.

Assuming you actually did start with 2 x 2TB, you are growing ~6TB in this step. So you could replace one of the 2 TB drives with a 4 TB model in the future, but that is as far as you can take it.

Disk manufacturers use power-of-10 units (1 000 000 000 000 bytes = 1 TB). Windows and many other software platforms (including the ultra) use power-of-2 units (1 099 511 627 776 bytes = 1 TiB). mdgm is using TiB in his post, which is why the numbers might be a bit smaller than you expect.

Hi StephenB,

Would you please be more specific where 8TiB limit is coming from ? according to http://kb.netgear.com/app/answers/detail/a_id/24555 4.2.26 should support 16TiB (and more after factory reset)
I'm considering to expand the space on my ultra 4 NAS with 4x 4tb WD red in raid5. I know that the drives are not in the compatibility list but I'm going to give it a try. In the same time I don't want to run into any limitation on the SW side.

Thanks

StephenB wrote:

The key idea here is that the 8 TiB limit applies to the volume size, not the raw disk sizes. You will end up with an ~8TB volume, so you can't exceed the 8 TiB growth limit no matter where you started from. Assuming you actually did start with 2 x 2TB, you are growing ~6TB in this step. So you could replace one of the 2 TB drives with a 4 TB model in the future, but that is as far as you can take it. Disk manufacturers use power-of-10 units (1 000 000 000 000 bytes = 1 TB). Windows and many other software platforms (including the ultra) use power-of-2 units (1 099 511 627 776 bytes = 1 TiB). mdgm is using TiB in his post, which is why the numbers might be a bit smaller than you expect.

crond wrote:
Would you please be more specific where 8TiB limit is coming from ? according to http://kb.netgear.com/app/answers/detail/a_id/24555 4.2.26 should support 16TiB (and more after factory reset)

The 8TB limit relates to online expansion and it is relative to the capacity when you last did a factory default. So if you started with e.g. a volume of 1.8TB you couldn't expand past 9.8TB. If you started with a volume capacity of e.g. 11TB then the 16TB limit would be encountered before the 8TB online expansion limit.

You can do a factory default with disks in place to get a volume larger than 16TB in capacity. For the 16TB limit to be an issue with a 4-bay NAS you would need e.g. 6TB disks. Or 5TB disks with a single RAID-0 volume (something I certainly would not recommend).

crond - 4x4TB would give you a 12 TB volume (10.9 TiB). So if your initial volume size (last default or initial install) was less than 2.9 TiB, then you would hit the 8 TiB growth limit..

Thanks for details.. that answers my questions

mdgm wrote:

crond wrote: Would you please be more specific where 8TiB limit is coming from ? according to http://kb.netgear.com/app/answers/detail/a_id/24555 4.2.26 should support 16TiB (and more after factory reset) The 8TB limit relates to online expansion and it is relative to the capacity when you last did a factory default. So if you started with e.g. a volume of 1.8TB you couldn't expand past 9.8TB. If you started with a volume capacity of e.g. 11TB then the 16TB limit would encountered before the 8TB online expansion limit. You can do a factory default with disks in place to get a volume larger than 16TB in capacity. For the 16TB limit to be an issue with a 4-bay NAS you would need e.g. 6TB disks. Or 5TB disks with a single RAID-0 volume (something I certainly would not recommend).

StephenB wrote:
crond - 4x4TB would give you a 12 TB volume (10.9 TiB). So if your initial volume size (last default or initial install) was less than 2.9 TiB, then you would hit the 8 TiB growth limit..

my initial install was 4x2tb in raid5 -> 6tb total. I'm happy with raid but it's been up and running for over 3 years nonstop and Load/unload cycles on disks are over 1.2M or 400% of what WD recommends and warranty ended this month, so time to change them before they fail. I'm thinking about going with 4tb which should give me 12tb, so theoretically I should be able to replace disks and grow volume. I guess it will take me a week+ to replace disks one by one / rebuild raid5 / grow volume.
Do you know any side effects or caveats that I should be aware of ?

Thanks!

Have you heard of wdidle3?
What model wd disks are you using?
Are the other smart stats for the 3 wd drives ok?

If you need to expand that's a good reason to replace the disks, I wouldn't do it simply because of the load/ unload cycles.