I/O question

["William A. Mahaffey III" <wam%hiwaay.net@localhost>]

I have a newly minted & commissioned NetBSD 6.1.5 server, featuring a 
3.6 TiB raidframe RAID5 mounted as /home. I decided to check I/O 
performance as follows:

[wam@4256EE1, ~, 5:48:00pm] 408 % time dd if=/dev/zero of=./testfile 
bs=16k count=32768
32768+0 records in
32768+0 records out
536870912 bytes transferred in 45.772 secs (11729243 bytes/sec)
 whew !!!! that took (0.096 cpu + 2.585 sys) sec., 0:45.77 elapsed time 
tot, 5.8% CPU efficiency
        (0 text, 0 data, 0 max) KB, (0+25) io, 0 pfs + 0 swaps
[wam@4256EE1, ~, 5:48:48pm] 409 %

The RAID in question has 4 active drives, 1 parity drive & 1 spare, 
created from identical ~900 GiB partitions on each of 6 7200 RPM 1 TB 
SATA3 HDD's. Those drives purportedly ave platter I/O speeds of around 
120 MiB/s (observed on other boxen). With 4 drive in parallel, that 
would be 480-ish MiB/s sustainable, under ideal conditions. I see about 
11 MiB/s above. That implies somewhat non-ideal conditions, which might 
not be surprising :-/. I *thought* I setup the RAID for reasonably 
optimum performance during provisioning of the machine, as 
breath-takingly/tediously documented onlist. What sort of online 
diagnostics can I do (dumpfs, etc.) on the mounted filesystem to assess 
where I might reconfigure/tune the RAID for better performance. I logged 
in using SSH as my regular user, then su'ed to root, so I (think I) need 
to keep the fs mounted. Any clues appreciated. TIA & have a good one.


--

	William A. Mahaffey III

 ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                           -- Gen. George S. Patton Jr.