Managing RAID on Linux

Hardware Considerations

Whether you choose to use kernel-based software RAID or buy a specialized RAID controller, there are some important decisions to make when buying components. Even if you plan to use software RAID, you will still need to purchase hard drives and disk controllers. The first step is to determine the ultimate size of your array and figure out how many drives are necessary to accommodate all the space you need, taking into account the extra space required by the level of RAID you choose. Don’t forget to factor the eventual need for hot-spares into your plan.

Choosing the right components can be the hardest decision to make when building a RAID system. If you’re building a production server, you should naturally buy the best hardware you can afford. If you’re just experimenting, then use whatever you have at your disposal, but realize that you may have to shell out a few dollars to make things work properly.

Several factors will ultimately affect the performance and expandability of your arrays:

• Bus throughput

• I/O channels

• Disk protocol throughput

• Drive speed

• CPU speed and memory

Computer architecture is a vast and complicated topic, and although this book covers the factors that will most drastically impact array performance, I advise anyone who is planning to build large-scale production systems, or build RAID systems for resale, to familiarize themselves thoroughly with all of the issues at hand. A complete primer on computer architecture is well beyond the scope of ...