[RESEND] Benchmark of I/O multiplexing with LZO/snappy compression

Hello,

I evaluated I/O multiplexing together with paralell compression in two
kinds of formats: lzo and snappy.

In summary:
- By 8-dimentional I/O multiplexing, thoughtput is 5 times as quick as
  the 1-dimentional: For snappy, 1TB copy takes 25min.
- For randomized data, snappy is as quick as raw, e.g. no compression
  case.
- lzo consumes more CPU time than snappy, but it could probably be
  better for quicker CPUs and more sparse data; another kind of bench
  is required.

In advance, any comments are appreciated.

Notice: Also, I'm sorry that I cannot attach source files I used in
this benchmark, fakevmcore.c and nsplit.c, due to ``suspicious
header'' warning from mail server; it requires moderator's approval
for the mail to get posted, but no one reacts... So I resend this mail
without any attachment.

* Environments

- PRIMEQUEST 1800E2
  - CPU: Intel Xeon E7-8870 (10core/2.4GHz) x 2 sockets
  - RAM: 32GB
- DISKS
  - MBD2147RC (10025rpm) x 4
  - ETERNUS DX440: Emulex 8Gb/s fiber adapters x 4