After getting my Coraid SAN hardware up and running I was having trouble deciding on how to use it. I mean it does the RAID stuff great but it doesn't have the ability to split up the space dynamically or shrink it at will. For that I needed LVM (Logical Volume Management) so I installed the Debian LVM2 package and went to work. I found an excellent resource on the subject of Linux, LVM, & RAID setup and followed it pretty closely. The only changes I made were to the RAID portion and that was because I had the Coraid doing all my heavy lifting.

So instead of using mdadm I created the RAID by typing the following line on the Coraid console.

make raid5 0.0-2

Since I have 4 physical disks in my SAN at the moment, this gives me a single RAID5 LUN (Logical Unit Number) and a hot swappable spare. This shows up on my Debian server as /dev/etherd/e0.0. I then initialized my new device as a physical volume, added it to a pv group, and created my first logical volume.

I am currently in the process of testing different file systems (JFS, ReiserFS, ex3) to find out which one performs the best and has the best reliability. I'm also testing a hardware failure by yanking out a disk in the middle of some operations. It should work fine and continue like nothing happened. If it doesn't, I would rather find out now when I don't have real data on it instead of 6 months from now when it could really cause some problems.

One more thing I found on another site was using a separate mirror with 3 disks as an off-site backup plan. Mount 2 of the disks in a RAID1 configuration and dump all of your backup data there. Then when you want to off-site your backups just yank one of the disks out and replace it with the spare. By taking the freshly yanked disk home or to your Mom's house you have a backup that can survive almost anything. Just do this 2-3 times a week and your golden.

I knew this SAN thing would come in handy...