RAIDZ2 questions

[pararesqcue]

QUESTION FOR YOU !

I am locate in Montreal (Province of Quebec, CANADA)

I am planning to build a storage server, storage data only, with FreeNAS. Idea is to get four (4) disks in raid kind of 6. So, your software seem to do it by using Raid Z2, as I understand. Correct me if I'm wrong. Unless there is another solution for those disks. My goal is parity double protection, if a disk failed.
I also understand FreeNAS will do it adequatly for data storage protection.

But what about disk capacity?
If one of the four (4) disks fail, I think I will just have to replace it and it get rebuild by himself. If two (2) disks fail on four (4) disks, does Raid Z2 is the good choice for that?

Also, if as exemple I put four(4) disks of 500Gb and one of it fail, the only disk I get in hand is an 1Tb, I gess the system will rebuild adequatly. But does it will get rebuilt in 500 Gb like the others, skipping at the same time the 500 resting of the 1Tb (losing 500Gb), or does FreeNAS will rebuilt it for the same 500 Gb space on keeping the 500Gb resting on 1Tb still available for future space capacity? In the sens of changing step by step each 500 Gb disk to 1TB for growing storage capacity. Is is possible with FreeNAS?

Synology NAS system call it hybrid Raid. Does Raid Z2 or other do the same?

Hoping a precise answer.

Pierre Lessard

 

[Ericloewe]

So, your software seem to do it by using Raid Z2, as I understand.

Yes, RAIDZ2 is broadly equivalent to RAID6 in traditional RAID parlance.

If one of the four (4) disks fail, I think I will just have to replace it and it get rebuild by himself. If two (2) disks fail on four (4) disks, does Raid Z2 is the good choice for that?

Yes, that's the whole point of having two disks' worth of redundancy.

Also, if as exemple I put four(4) disks of 500Gb and one of it fail, the only disk I get in hand is an 1Tb

The vdev's capacity will be determined by the smallest disk, so capacity will not change after you replace a single disk with a larger one. Once you have replaced the last disk with a larger one, the vdev will grow if the autoexpand flag is set (it is by default).

In the sens of changing step by step each 500 Gb disk to 1TB for growing storage capacity. Is is possible with FreeNAS?

See above.

Synology NAS system call it hybrid Raid. Does Raid Z2 or other do the same?

Not being familiar with their terminology, I would expect it to mean something more. Soon (tm) it will be possible to add disks to existing RAIDZ vdevs to expand their capacity (removal will not be possible).