[OpenIndiana-discuss] raidz2 as compared to 1:1 mirrors

[reader]

Judah Richardson <judahrichardson at gmail.com> writes:


[...]

> Usable storage, S = (N-p)C, where:

> N = total number of disks
> p = number of parity disks
> C = (lowest) capacity per disk

Thanks for the formula


[...]

> TL,DR: Yeah the results you're getting should be correct.

There were 12 lines... Sorry if so poorly forumulated and written that
12 lines is TL


[...]
Excellent help JR .. thx

Jason Matthews <jason at broken.net> writes:

> 11 TB is about right. Your 2TB disks will be "smaller" by nature of
> reporting differences. Much of that is difference between how drive 
> manufacturers report a megabyte as 1,000,000 bytes and computers
> report a megabyte 1048576 bytes.
>
> In a nutshell, in your raidz2 vdev you have eight drives. Two drives
> are for parity so you have six drives for data. 6*2 = 12TB less the 
> accounting differences gives you 11TB and change.
>
> This gives you space at the price of performance. You will have the
> write performance of roughly one disk and the read performance of six 
> disks, excluding cache of course. That might be peachy for your
> application or it might not.  The best part is, you get to judge.
>
> I almost never use raidz* if performance is a consideration.

[...]

Excellent help .. thx for you time... good to hear from a couple of
old hands.