Something I’ve been wanting to do for a while is to put redundancy back in our iTunes server. Originally, I had two LaCie 500 GB drives that were mirrored (RAID 1). (See (a) in the figure below.) The iTunes library grew as we bought more seasons of TV shows, movies, and music, and we finally ran out of space. For a while I was copying older stuff to another drive but that quickly lost its luster.
The "second generation" of our iTunes server had no redundancy; just a single 1TB Western Digital My Book Home Edition drive. Now everything was back on one drive. I started burning DVDs of the files but a family of four with different tastes in audio and video make it really hard to keep up. Plus, we were over the 80% mark on drive utilization so…
In accordance with Moore’s Law, drive capacities goes up, prices come down. What cost me $159 last Christmas now costs me $119. I bought three (3) more of the WD 1TB drives and hooked them up. This time though, I grouped them a bit differently.
First, I created two sets of two drives each. (See (b) in the figure above.) Each set is configured to be Striped (RAID 0) so that half the data lives on one drive and the other half of the data lives on the other drive. This more for performance that data protection (no check bits). Then I Mirrored (RAID 1) the two sets to get redundancy. In theory, if any single drive fails, you can replace it and rebuild the RAID.
Is RAID 1+0 better performance-wise than RAID 0+1? I don’t know. Apple’s computers1 come with software-based RAID built into the OS. Software-based RAID is going to be slower than hardware-based RAID solutions. Add in the lag time from USB 2.0 or FireWire 400 and it may not matter in the end.
In any case, I have a 2 TB RAID-enabled set-up that should provide enough storage through say, Christmas?
1. Apple’s Xserve offers RAID 5 support in hardware.