Continuing a previous thread, here is data from a recent RAID6 JackRabbit test. This is a 24 bay, 24 TB machine, with 64 GB ram, 8 processor cores, 1x DDR IB port, 2x GbE.
`[root@jackrabbit ~]# iozone -s 32g -r 2048 -t 4 -F /big/f.0 /big/f.1 /big/f.2 /big/f.3
Iozone: Performance Test of File I/O
Version $Revision: 3.315 $
Compiled for 64 bit mode.
Build: linux
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, Gavin Brebner,
Jean-Marc Zucconi, Jeff Blomberg, Benny Halevy,
Erik Habbinga, Kris Strecker, Walter Wong, Joshua Root.
Run began: Mon Feb 23 13:08:05 2009
File size set to 33554432 KB
Record Size 2048 KB
Command line used: iozone -s 32g -r 2048 -t 4 -F /big/f.0 /big/f.1 /big/f.2 /big/f.3
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.
Throughput test with 4 processes
Each process writes a 33554432 Kbyte file in 2048 Kbyte records
Children see throughput for 4 initial writers = 1352042.62 KB/sec
Parent sees throughput for 4 initial writers = 1220898.43 KB/sec
Min throughput per process = 329863.62 KB/sec
Max throughput per process = 347089.50 KB/sec
Avg throughput per process = 338010.66 KB/sec
Min xfer = 31891456.00 KB
Children see throughput for 4 rewriters = 947072.89 KB/sec
Parent sees throughput for 4 rewriters = 886211.49 KB/sec
Min throughput per process = 235013.97 KB/sec
Max throughput per process = 240611.41 KB/sec
Avg throughput per process = 236768.22 KB/sec
Min xfer = 32804864.00 KB
Children see throughput for 4 readers = 909722.69 KB/sec
Parent sees throughput for 4 readers = 909515.58 KB/sec
Min throughput per process = 205315.34 KB/sec
Max throughput per process = 235982.22 KB/sec
Avg throughput per process = 227430.67 KB/sec
Min xfer = 29194240.00 KB
Children see throughput for 4 re-readers = 989195.89 KB/sec
Parent sees throughput for 4 re-readers = 988841.08 KB/sec
Min throughput per process = 228572.11 KB/sec
Max throughput per process = 256498.69 KB/sec
Avg throughput per process = 247298.97 KB/sec
Min xfer = 29915136.00 KB
`
Not bad … about a 10-15% performance bump for most things, with a nearly 100% bump for writing. Again, these are 4 threads, each working with 32GB, so 128 GB total data transfer. 2x ram.