How to set up 4 disks with 2 striped and then mirrored

[Stephan Hochhaus]

Hello forum,

I have a small installation with 4 drives (2TB each) and I am trying to understand how I can create two pairs of striped disks which I can mirror then (basically a RAID-10 I would think). In the volume manager I can only select drives and then either mirror or stripe. How do I properly do this using the UI? Or do I need to use the command line to achieve this?

Here's what I tried so far, but the result is not what I expected (5.4 TB instead of 4 TB). First I created a volume with two drives and selected mirrored, then I extended the volume with two disks and selected striped.
Is that the proper way to do it?

Any help is greatly appreciated as I am somewhat new to ZFS (yet I know that I do not want a RAIDZ, but a simpler form since mirroring should be sufficient for my home use).

 

[paleoN]

Here's what I tried so far, but the result is not what I expected (5.4 TB instead of 4 TB). First I created a volume with two drives and selected mirrored, then I extended the volume with two disks and selected striped.
Is that the proper way to do it?

No, select mirror the second time as well. This will create your striped mirrors.

 

[Stephan Hochhaus]

Thanks, that looks about right. Got 3.6 TB space on the volume now. Let's see how far I can take it from here ;-)

 

[rguyler]

Thanks, that looks about right. Got 3.6 TB space on the volume now. Let's see how far I can take it from here ;-)

To be technically correct, when you stripe disk pairs first then mirror the pairs it's called RAID 0/1, not RAID 10, which builds mirrors first then stripes across them.

The difference in the setup is the order that you stripe and mirror. However, the difference in the end product is significant. When you lose a drive in RAID 10, the rebuild is limited to the one mirror set with the failed drive and does not affect the entire RAID group. When you lose a drive in RAID 0/1 the rebuild affects the entire RAID group, which subjects all the drives to the rebuild. For that reason, I recommend building RAID1 groups and then add them to a pool, which will stripe across the RAID groups to create RAID 10. Avoid RAID 0/1 if possible, especially with SATA drives.

 

[Ericloewe]

So that nobody else gets the wrong idea due to this thread:

You cannot stripe two 500GB drives, then mirror them with a 1TB drive to get 1TB of space. ZFS doesn't work like that.