dmcrypt/luks is used on top of the raid. The performance of the i5 is not great, despite hardware aes. Should not be this numbers a bit higher than 158 MB/sec?

~/httptunnel-3.3/ hdparm -t --direct /dev/md1

/dev/md1:
Timing O_DIRECT disk reads: 936 MB in 3.00 seconds = 311.67 MB/sec

~/httptunnel-3.3/ hdparm -t --direct /dev/mapper/evol

/dev/mapper/evol:
Timing O_DIRECT disk reads: 476 MB in 3.01 seconds = 158.30 MB/sec

cat /proc/cpuinfo | grep -E (model name|aes)
model name      : Intel(R) Core(TM) i5 CPU         660 @ 3.33GHz
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt aes lahf_lm ida arat dts tpr_shadow vnmi flexpriority ept vpid