ZFS performance

[fluca1978]

Hi all,
today I moved almost 30 GB from a ZFS dataset to another within the same pool, and the following is a sample of the iostat while doing the process:

tty da0 ada0 ada1 cpu
tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id
0 16 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0 0 1 0 99
0 47 0.00 0 0.00 0.00 0 0.00 55.93 177 9.69 0 0 3 0 97
0 16 0.00 0 0.00 0.00 0 0.00 34.55 288 9.72 0 0 5 0 94
0 16 0.00 0 0.00 0.00 0 0.00 73.51 495 35.56 0 0 5 1 94
0 16 0.00 0 0.00 0.00 0 0.00 74.84 321 23.45 0 0 3 0 96
0 16 0.00 0 0.00 0.00 0 0.00 3.28 11 0.03 0 0 1 0 99
0 16 0.00 0 0.00 0.00 0 0.00 46.30 310 13.99 0 0 3 0 96
0 16 0.00 0 0.00 0.00 0 0.00 14.09 301 4.14 0 0 4 0 96
0 16 0.00 0 0.00 0.00 0 0.00 10.82 327 3.46 0 0 3 0 97
0 16 0.00 0 0.00 0.00 0 0.00 86.56 343 29.02 0 0 4 0 96
0 16 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0 0 1 0 99
0 16 12.47 31 0.38 0.00 0 0.00 84.10 18 1.51 5 0 2 0 93
0 16 0.00 0 0.00 0.00 0 0.00 14.37 41 0.58 0 0 1 0 99
0 16 0.00 0 0.00 0.00 0 0.00 20.84 181 3.68 0 0 2 0 98
0 16 0.00 0 0.00 0.00 0 0.00 13.77 219 2.94 0 0 1 0 98
0 16 0.00 0 0.00 0.00 0 0.00 22.92 294 6.58 0 0 5 0 95
0 16 0.00 0 0.00 0.00 0 0.00 12.74 215 2.67 0 0 2 0 98
0 16 12.00 0 0.00 0.00 0 0.00 74.47 392 28.49 0 0 5 0 95
0 16 0.00 0 0.00 0.00 0 0.00 42.78 2 0.08 0 0 1 0 99
0 16 0.00 0 0.00 0.00 0 0.00 55.05 41 2.20 0 0 1 0 99
0 16 0.00 0 0.00 0.00 0 0.00 45.93 19 0.84 0 0 1 0 99


As you can see there are several moments when the number of transactions are low, so I was guessing what could be the cause and this behavior is normal. My nas is running 8.2-RELEASE and has 8 GB of memory. The zpool is made by four disks for a total storage of almost 8 TB:

# zpool status
pool: RPOOL
state: ONLINE
scrub: none requested
config:

NAME STATE READ WRITE CKSUM
RPOOL ONLINE 0 0 0
raidz1 ONLINE 0 0 0
ada1p2 ONLINE 0 0 0
ada2p2 ONLINE 0 0 0
ada3p2 ONLINE 0 0 0
ada4p2 ONLINE 0 0 0


comments?