Multiple Hard Drives

Disk input/output is usually the slowest part of a computer. If you have more than one hard drive, you can use those drives to accelerate your system performance.

First, make sure that each drive is on its own port. SCSI and SATA drives usually accommodate one drive per port (unless you specifically use a port multiplier), but IDE drives usually attach two devices per port. Each port has a maximum throughput. It does no good to attach two fast drives to one port, as the drives compete for the one port’s throughput.

In general, when you have multiple drives, you want to split the read and write activity between the drives. I usually put the data I’m serving on one disk and the important system files on another. If I’m building a database server, I might dedicate one disk to swap space and /var, while assigning all other partitions to the other disk.

Split your swap space between the drives. Be sure that at least one partition is large enough to hold the contents of your physical RAM, so that OpenBSD can do a crash dump if needed. OpenBSD cannot split a crash dump between two different swap partitions.

If you’re a more experienced OpenBSD user, you can use multiple hard drives to create a redundant disk with software RAID. We’ll cover how to do that in Chapter 9.

If your second drive is much slower than your main system drive, don’t bother using it. A computer runs only as fast as its slowest component, so adding that old IDE drive to your SATA system will drag down the whole machine. Not only will its presence degrade performance for the whole system, but it’s also probably much older than your main drive and far more likely to fail.