Calculating ZFS space

[signal15]

Say I have 8 drives:
- Four 1TB
- One 1.5TB
- One 750G
- Three 500G

If I put all of these in a RAIDZ2 pool, how much space should I have? I put them all in a pool, and I ended up with 2.7TB (2.6TiB). Obviously, ZFS is able to use different size drives. But I'm wondering why I don't have more space. What's not being used here?

I also know that this isn't the best configuration for performance. I'm not worried about that, I'm simply storing large files that are infrequently accessed, so performance is not an issue. A write speed test to it showed around 150MB/sec (1200Mbit/sec). That's fine for what I'm doing.

If I take out a 500GB drive and put in a 4TB drive, how much will my available storage go up? What about with a 3TB drive?

I'm just trying to understand how things are allocated so I can plan for buying larger drives.

 

[cyberjock]

Your zpool size is limited to the smallest of all of your drives. In your case, your 500GB drives are limiting your entire array. Knowing this....


The answer to:

If I take out a 500GB drive and put in a 4TB drive, how much will my available storage go up?

Not a bit. You'd have to replace all 3 of your 500GB drives with something bigger to see any size increase.

What about with a 3TB drive?

Not a bit. Again, you'd have to replace all 3 of your 500Gb drives with something bigger to see any size increase.

If you had read my guide(link in the sig) you would have understood that you are always limited to the smallest disk. The law of conservation of data strikes again.

And, if you had read the manual, section 1.4.4 says:

Further, when creating a RAIDZ, only the size of the smallest disk will be used on each disk.