Here is a quick snipped on how to benchmark Disk I/O with dd.
time sh -c "dd if=/dev/zero of=/home/rchapin/test.zeros bs=1024k count=10000 && sync" 10000+0 records in 10000+0 records out 10485760000 bytes (10 GB) copied, 81.4124 s, 129 MB/s real 1m21.950s user 0m0.810s sys 0m5.474s
Will do a write test of 10GB.
You can do a similar test and read from that file generated and write to another file or /dev/null to get an idea of the read speeds.
See the this link for more information.