D.8 Number of Disk Spindles

In this section, I compare Squid's performance for different number of disk drives (spindles). These tests are from the Linux system with the aufs storage scheme and ext2fs filesystems.

Table D-6 and Figure D-6 summarize the results. The test with no disk drives has the best throughput, but the worst response time and hit ratio. Note that Squid does serve a few cache hits from memory, so the hit ratio isn't zero.

Table D-6. Comparison of 0-3 disk spindles on Linux with aufs

#Disks	Throughput	Response time	Hit ratio
	332.1	2.99	0.4
3	109.6	1.44	56.2
2	85.3	1.49	53.9
1	66.0	1.50	53.5

Figure D-6. Benchmarking results for 0, 1, 2, and 3 disk drives on Linux with aufs

The primary purpose of these tests is to show that Squid's performance doesn't increase in proportion to the number of disk drives. Excluding other factors, you may be able to get better performance from three systems with one disk drive each, rather than a single system with three drives.