How to set up 2-way and 3-way mirrors.

[JenWest1919]

Hours of Googling since last night hasn't revealed any clear, concise information on doing this within FreeNAS.

Would someone be able to confirm whether or not my assumptions are correct?

I have six, 8TB disks in my setup.

I am assuming a "2-way" mirror would look like this:
http://i.imgur.com/CUH8jgb.jpg

I am assuming a "3-way" mirror would look like this:
http://i.imgur.com/I1goClA.jpg

I am also assuming that in order to increase the size of a 3-way mirror, you need 3 more disks, and a 2-way mirror, only 2 more.

Are all of my assumptions correct?

Thank you!

 

[danb35]

You've posted the same image twice, with the same caption. That configuration will give you three mirrors, of two disks each, striped together. A "3-way" mirror would have three columns and two rows, and would consist of two mirrors, of three disks each, striped together.

I am also assuming that in order to increase the size of a 3-way mirror, you need 3 more disks, and a 2-way mirror, only 2 more.

If you wanted to keep the same level of redundancy, this would be correct. But there's nothing inherent in ZFS that would keep you from striping a two-disk mirror with a pair of three-disk mirrors, or vice versa. Or even striping in a 12-way mirror, as another member here recently did.

 

[JenWest1919]

You've posted the same image twice, with the same caption. That configuration will give you three mirrors, of two disks each, striped together. A "3-way" mirror would have three columns and two rows, and would consist of two mirrors, of three disks each, striped together.

If you wanted to keep the same level of redundancy, this would be correct. But there's nothing inherent in ZFS that would keep you from striping a two-disk mirror with a pair of three-disk mirrors, or vice versa. Or even striping in a 12-way mirror, as another member here recently did.

Oops, sorry. I updated the post.

That is correct the configuration I posted will give me three mirrors - but they're all 2 way mirrors, correct?

 

[danb35]

but they're all 2 way mirrors, correct?

Yes, as I said, it's three mirrors of two disks each.

 

[Arwen]

One easy way to look at it, is the expected capacity. Do the math.

I screwed up a server build a few years ago. Wanted to create a 3 vDev 2 way Mirror pool.
But, ended up with a 2 vDev 3 way Mirror pool. Caught it before it went into production
because the available space did not match what I expected.

Got confused because Solaris' DiskSuite's display is different, and had been making and
fixing dozens of DiskSuite Mirrors.