I recently bought a Western Digital RED drive to replace one of my old Western Digital Caviar Green drives in my FreeNAS storage. As previously mentioned I run a RAIDZ wich is comparable to a RAID-5 so I can do this without data loss.
The RED drives are supposed to be specifically designed for use in 1-5 drive NAS situations and have gotten pretty good reviews so even though it is a bit pricy I wanted to give it a go. In perspective the drive is only 100SEK cheaper then the Caviar Greens were two and a half years ago when I bought those.
Before replacing the drive it is recommended to scrub the pool to make sure everything is in order.
One thing to note is that in order for ZFS to accept a new drive as a replacement it has to have an LBA count that is equal or higher than the old drive. Look it up on the old drive:
[root@void] ~# camcontrol identify ada0 | grep LBA48
LBA48 supported 3907029168 sectors
Then verify with the datasheet for the new drive before purchase. In my case this.
This is a quick step by step of how I did it using the GUI. The next drive getting replaced will be so via cli only.