autoexpanding zfs on adding larger drives

madivad · 03-18-2008, 05:15 AM

I have just finished a round of testing which has left me a little confused.

I was under the impression that if you increased the size of all the harddrives in a zfs pool/raidz setup, that once you had replaced the last small drive, the extra space of the new drives would be available.

After running a test, I have found that not to be the case. Can someone tell me what I am doing wrong?

First off, I created 5 100mb files

Code:

# mkfile 100m /disk1
# mkfile 100m /disk2
# mkfile 100m /disk3
# mkfile 100m /disk4
# mkfile 100m /disk5

Then I created 5x 200mb files

Code:

# mkfile 200m /disk6
# mkfile 200m /disk7
# mkfile 200m /disk8
# mkfile 200m /disk9
# mkfile 200m /disk10

I created the pool:

Code:

# zpool create test raidz /disk1 /disk2 /disk3 /disk4 /disk5

End result:

Code:

# ls -lrt disk*
-rw------T 1 root root 104857600 Mar 17 14:59 disk1
-rw------T 1 root root 104857600 Mar 17 15:00 disk2
-rw------T 1 root root 104857600 Mar 17 15:00 disk3
-rw------T 1 root root 104857600 Mar 17 15:01 disk4
-rw------T 1 root root 104857600 Mar 17 15:02 disk5
-rw------T 1 root root 209715200 Mar 17 15:05 disk6
-rw------T 1 root root 209715200 Mar 17 15:05 disk7
-rw------T 1 root root 209715200 Mar 17 15:05 disk8
-rw------T 1 root root 209715200 Mar 17 15:05 disk9
-rw------T 1 root root 209715200 Mar 17 15:05 disk10

I then one by one replaced all the (pseudo) drives with the larger ones

Code:

# zpool replace test /disk1 /disk6
# zpool replace test /disk2 /disk7
#... and so on

I did a zfs list between each change, and there was no change (as expected), but when I changed the last drive, I thought the new size would be visible. It wasn't.

Code:

# zpool status test
  pool: test
 state: ONLINE
 scrub: scrub completed with 0 errors on Mon Mar 17 15:04:05 2008
config:

        NAME         STATE     READ WRITE CKSUM
        test         ONLINE       0     0     0
          raidz1     ONLINE       0     0     0
            /disk6   ONLINE       0     0     0
            /disk7   ONLINE       0     0     0
            /disk8   ONLINE       0     0     0
            /disk9   ONLINE       0     0     0
            /disk10  ONLINE       0     0     0

errors: No known data errors


# zpool list test
NAME   SIZE   USED  AVAIL    CAP  HEALTH  ALTROOT
test   476M  12.7M   463M     2%  ONLINE  -


# zfs list test
NAME   USED  AVAIL  REFER  MOUNTPOINT
test  10.1M   338M  10.0M  /test

I now have 5 drives of 200mb each, 1gb (confirmed in the ls back up the page a bit). I would have expected 750-800mb, but there is less than 350mb there. I threw a 10mb file in there for good measure and even tried scrubbing it. Are my commands wrong? I performed a scrub, but to no avail? What do you have to do for the zfs/zpool to update?

jlliagre · 03-19-2008, 03:42 AM

Indeed, there seem to be no way to enlarge the raidz in site.
The alternative would be to create a new pool with the new devices and migrate the data from the older to the newer. That would require twice more disk slots during the process though.