[Tig] Can someone help me with my drive array?

[Bob Friesenhahn]

I am setting up a drive array (Sun StorageTek 2540) which is fitted 
with 12 300GB 15KRPM SAS drives.  There are dual controllers and dual 
4Gbit FC connections to my host.  This has been a long time comming 
and at times I experienced the agony of defeat (first unit was smashed 
in shipping), but it is finally here and apparently working.  The 
drive array is in my home, which is probably an unusual location.  The 
drive array is a present to myself to support GraphicsMagick 
development.

I have spent several days now working to make sure that the fiber 
channel connection is solid (it was bouncing) and to understand 
performance issues.  Unfortunately, I don't understand the performance 
values that I am seeing.  It seems that regardless of what RAID 
configuration I use (even RAID 0 with 12 drives), the single-file 
write I/O rate (according to 'iozone') is in the range of 170-200 
MB/second.  I was hoping to do 1/3 better than that.  There is a 
bottleneck somewhere.  An odd thing, is that other substantial 
I/O activity on the filesystem does not seem to impact iozone results.

I don't know exactly what iozone is doing, but every once in a while 
the disk activity (as reported by the OS) seems to cease for 10 or 20 
seconds, yet the numbers printed by iozone are fairly consistent.

Can someone here with experience with SAN and drive array performance 
help me understand what is going on and the performance levels I 
should actually expect?  The output from an iozone run is attached.

Thanks,

Bob
======================================
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

 	Iozone: Performance Test of File I/O
 	        Version $Revision: 3.283 $
 		Compiled for 64 bit mode.
 		Build: Solaris10gcc-64

 	Contributors:William Norcott, Don Capps, Isom Crawford, Kirby Collins
 	             Al Slater, Scott Rhine, Mike Wisner, Ken Goss
 	             Steve Landherr, Brad Smith, Mark Kelly, Dr. Alain CYR,
 	             Randy Dunlap, Mark Montague, Dan Million,
 	             Jean-Marc Zucconi, Jeff Blomberg, Benny Halevy,
 	             Erik Habbinga, Kris Strecker, Walter Wong.

 	Run began: Thu Feb 14 08:52:33 2008

 	Auto Mode
 	Using Minimum Record Size 64 KB
 	Using Maximum Record Size 512 KB
 	Using minimum file size of 16777216 kilobytes.
 	Using maximum file size of 33554432 kilobytes.
 	Command line used: iozone -a -i 0 -i 1 -y 64 -q 512 -n 16G -g 32G
 	Output is in Kbytes/sec
 	Time Resolution = 0.000001 seconds.
 	Processor cache size set to 1024 Kbytes.
 	Processor cache line size set to 32 bytes.
 	File stride size set to 17 * record size.
                                                             random  random    bkwd  record  stride
               KB  reclen   write rewrite    read    reread    read   write    read rewrite    read   fwrite frewrite   fread  freread
         16777216      64  196815  115715   495561   382353
         16777216     128  180500  179898   333415   332368
         16777216     256  179846  179635   333178   333090
         16777216     512  177443  181405   332257   346124
         33554432      64  192275  112841   332105   332730
         33554432     128  179471  174863   331858   332041
         33554432     256  177570  194285   332262   332414
         33554432     512  200085  179983   331898   331971

iozone test complete.