I'm currently planning on installing FreeBSD 9 on my home server. The machine has 4x 1.5TB disks, and at some point, when HDD prices drop I'll be upgrading to something bigger, perhaps 3TB.

The disks are connected to an IBM ServerRaid m1015 in IT mode, this card has room for up to eight disks. Now here is the problem, currently the 4x 1.5TB will be connected to the m1015. Then when prices drop I'll be adding something like 4x 3TB, also connected to the m1015. No problem yet, I can just run 2 raidz2 vdevs and put them in the same pool.

But, at some point the 1.5TBs will start to break, or I will have to upgrade them when the pool runs out of space. So I started researching if it's possible to expand a raidz vdev, and I found several pages explaining the same procedure, like this on SF: How to upgrade a ZFS RAID-Z array to larger disks on OpenSolaris?.

So I went a head and tried that in vmware, I installed FreeBSD 9 and created 6 virtual disks, 3 of 1GB each and 3 of 10GB each. After building a raidz vdev of the 1GBs I replaced them one by one with the 10GB, but the pool did not increase in size.

Is this a limitation of the ZFS implementation in FreeBSD? Or am I just doing something wrong?