How to setup mirror.

[helloha]

Hi,

I have 6x 3TB disks.

I want create 2 vdevs each containing 3 disks and put them in stripe.

Then I would mirror both vdevs.

Can anyone tell me how to set this up in the GUI?

Do I have to create a striped vdev first and then expand with a mirror?

THX!
K.

 

[danb35]

You're looking at it backward. You'll set up three two-disk mirrors, and stripe those three mirrors together. Drag the slider in the GUI to three across and two down, and set the drop-down to mirror, IIRC.

 

[helloha]

If I do 3 across 2 down I only get 5.4 TB of usable space.

Code:

    NAME                                            STATE     READ WRITE CKSUM
    TSW-MIRROR-5.4TB                                ONLINE       0     0     0
     mirror-0                                      ONLINE       0     0     0
       gptid/61449c31-f683-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/63aec29c-f683-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/66135040-f683-11e4-8de0-001f2954783c  ONLINE       0     0     0
     mirror-1                                      ONLINE       0     0     0
       gptid/68609b30-f683-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/6ab8869f-f683-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/6d2364f8-f683-11e4-8de0-001f2954783c  ONLINE       0     0     0

   

But if I do 2 across 3 down I get 8.2 TB of usable space.

But in this scenario I'm somewhat confused. Am i mirroring 3 vdevs in this scenario?
And I don't understand how 1 vdev of 6TB mirrored 3 times generates 8TB of space?

Code:

 TSW-MIRROR 8.2TB                                ONLINE       0     0     0
     mirror-0                                      ONLINE       0     0     0
       gptid/3ae57524-f682-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/3d4c1557-f682-11e4-8de0-001f2954783c  ONLINE       0     0     0
     mirror-1                                      ONLINE       0     0     0
       gptid/3fb1715d-f682-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/41f88767-f682-11e4-8de0-001f2954783c  ONLINE       0     0     0
     mirror-2                                      ONLINE       0     0     0
       gptid/4452e0d8-f682-11e4-8de0-001f2954783c  ONLINE       0     0     0
       gptid/46bae8b8-f682-11e4-8de0-001f2954783c  ONLINE       0     0     0

Which route should I go? Only having 5.4TB is a lot to sacrifice for 9TB of disk space out of 18TB of raw disk space.

THX!
K.

 

[Bidule0hm]

In the first scenario you have 2 vdevs (mirrors of 3 drives) that are striped together. So you have 1/3 of the space for the data and 2/3 for parity.

In the second scenario you have 3 vdevs (mirrors of 2 drives) that are striped together so you have half the space for the data and the other half for parity (and I guess it's what you want) ;)

Also, be careful when you speak about the size because there is TB and TiB. TB is what the maketing dickheads use (like a 3 TB drive) and TiB is what all the other persons use (that's why you can't put more than about 2.7 TiB of data on a 3 TB drive).

 

[helloha]

I see, do you know what kind of redundancy I have in the second scenario? (I'm still confused about how a mirror out of uneven devices is possible :))

Can I lose one complete VDEV? Or only one disk in one VDEV?

But I guess no multiple disks out of different VDEV's.

THX!
K.

 

[Bidule0hm]

You can't lose any vdev in a pool if you don't want to lose the entire pool.

With a mirror (of 2 drives) you can lose 1 drive max.

With a 3 way mirror (mirror of 3 drives) you can lose 2 drives max.

A mirror with more than 2 drives is possible and the data is just copied to each drive. You can have a mirror with 2, 3, 4, ... drives. However it's pretty rare to have mirrors with 3 drives, let alone 4 or more...

 

[mjws00]

With 6 drives just use raidz2. If you want max IOPS than you will want 3 vdevs of 2 drives (striped mirrors), like your second example. Which will incur 3 drives parity instead of 2 with raidz2.

 

[helloha]

Yes I was going for maximum IOPS. Getting 350 MB/s write 450MB/s read with this setup. (second scenario). THX!