Тест на сервере от digitalocean.com
[root@wmail home]# dd if=/dev/zero of=tempfile bs=5M count=1024 conv=fdatasync,notrunc
1024+0 records in
1024+0 records out
5368709120 bytes (5.4 GB) copied, 28.0395 s, 191 MB/s
[root@wmail home]# dd if=tempfile of=/dev/null bs=5M count=1024
1024+0 records in
1024+0 records out
5368709120 bytes (5.4 GB) copied, 19.8854 s, 270 MB/s
===========================
[root@wmail home]# hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   12048 MB in  2.00 seconds = 6031.07 MB/sec
 Timing buffered disk reads:  432 MB in  3.02 seconds = 142.98 MB/sec
===========================
[root@wmail home]# sysbench --num-threads=16 --test=fileio --file-total-size=5G --file-test-mode=rndrw run
sysbench 0.4.12:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 16

Extra file open flags: 0
128 files, 40Mb each
5Gb total file size
Block size 16Kb
Number of random requests for random IO: 10000
Read/Write ratio for combined random IO test: 1.50
Periodic FSYNC enabled, calling fsync() each 100 requests.
Calling fsync() at the end of test, Enabled.
Using synchronous I/O mode
Doing random r/w test
Threads started!
Done.

Operations performed:  6003 Read, 3997 Write, 12800 Other = 22800 Total
Read 93.797Mb  Written 62.453Mb  Total transferred 156.25Mb  (32.599Mb/sec)
 2086.36 Requests/sec executed

Test execution summary:
    total time:                          4.7930s
    total number of events:              10000
    total time taken by event execution: 28.5906
    per-request statistics:
         min:                                  0.01ms
         avg:                                  2.86ms
         max:                                329.93ms
         approx.  95 percentile:               9.79ms

Threads fairness:
    events (avg/stddev):           625.0000/145.36
    execution time (avg/stddev):   1.7869/0.26