4x1Tb with RAIDZ2 gives 4Tb free space?

[riporto]

Hi all,
I've rebuild my server after an apparent disk crash deleting and formatting all my four 1Tb disks.
This time I'll try RAIDZ2, before i had RAIDZ1, disk space is not an issue for me so from the original 4Tb if I can use only 2Tb is ok for me.
I set up all as usual, build pool, virtual device and datasets and all is ok but, and there is a but, in pools/management and in the system home page it gives me free space 3.62Tb! What's that? With RAIDZ2 there should be less than 2Tb free space! No? What I did wrong???

[kenZ71]

Sounds more like a Raid setup.

Under Disks|ZFS|Configuration|Detected what do you see for Type?

[riporto]

[Snapshot]

I see the same with around 7.3TB free using 4 x 2TB drives in RAIDz1 so I think it is just reporting the total space available. I would expect to see the space decrease more quickly as data is copied to the RAID but I haven't checked this yet.

I can now confirm that this is what's happening - I copied a 117GB file to the RAIDz1 and the allocated space went up by 154GB. This is exactly the difference one would expect on a four-drive RAIDz1.

[riporto]

Hm in my previous configuration I had RAIDZ1 with the four 1Tb disks and in System>General I saw less than 3Tb available space, which is correct as with RAIDZ1 you will loose about one disk space.
I don't understand why with RAIDZ2 I see almost 4Tb free space when I should see about 2Tb...
I must have done something wrong in configuration (what???) or in the latest NAS4FREE version something has changed...

[Snapshot]

I see the same as you but with z1 so perhaps NAS4FREE has changed the way it reports disk space. I agree that showing the effective available space is more sensible.

[riporto]

I've tryed an "experiment" like yours Snapshot, I've copyed a 12Gb file on my RAIDZ2 server and I see 23.7Gb allocated space, almost double the dimension of the file I've copyed. As per your reasoning it should be correct as with RAIDZ2 I will loose double the space used.
Hope it is correct and all will work fine...