I recently started migrating servers with relatively low storage space requirements to SSDs. In many cases the HDDs that get replaced are much bigger than required and unfortunately the zpools have been configured to use all the available space. Since shrinking a pool is not supported by ZFS directly, the procedure is a little more elaborate.
We have a couple of cheap servers using a single 1 TB drive connected to the on-board Intel SATA controller and wanted to add a second hard drive to improve reliability. The following instructions show how to convert the ZFS pool into a mirrored pool without rebooting.
This blog post details how to replace a broken drive in the mfsBSD, FreeBSD 9.0 raidz2 ZFS setup discussed earlier. The process is relatively straightforward, but can be tricky if you never did it before.
As I explained in an earlier post, we had issues with one of our backup servers. I decided to do a complete reinstall and ended up using an LSI SAS 9211 controller running in initiator-target mode (IT firmware), so all eight disks show up as plain HBAs and can be used to form a zpool. After considering my options I decided to go with raidz2, which will provide a good balance of storage space and safety.
In my last post I wrote about how the Adaptec 5805 RAID controller was the wrong choice for our backup server. So I started some research, based on the following criteria:
One of the less maintained machines in our data center is a small backup server. It's basically sitting there, storing all those backups nobody really uses and slowly fills up its disk array. Once in a while somebody checks it manually to see if everything's in order (it has never been really connected to anything sitting on its own isolated VLAN).
The server uses an Adaptec 5805 controller, a product line I tried debugging and fixing a long time ago (see also http://lists.freebsd.org/pipermail/freebsd-bugs/2009-June/035612.html). Unfortunately back then our supplier stated that this is the only controller certified for this machine - so I gave in, hoping that a pretty much bored backup server won't have too much trouble keeping up with the little load it would get.
I was wrong.
