Re: Load distributed checkpoint

From: "Bruce Momjian" <bruce(at)momjian(dot)us>
> On an idle system, would someone dirty a large file, and watch the
disk
> I/O to see how long it takes for the I/O to complete to disk?

I ran "dd if=/dev/zero of=<file on DB disk> bs=8k count=`expr 1048576
/ 8`, that is, writing 1GB file with 8KB write()'s. It took about 175
seconds for the kernel to flush buffers. I'll put the result of
"iostat -x 5" which was started at the same time as dd. 175 seconds
means 35 rows with nonzero %util * 5 seconds of interval.

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util
sde 0.00 981.56 0.00 50.90 0.00 8439.28 0.00 4219.64
165.80 34.38 525.01 6.25 31.82
sde 0.00 25737.00 0.00 118.60 0.00 219820.80 0.00
109910.40 1853.46 6529.74 1587.08 8.43 100.02
sde 0.00 1912.97 0.00 127.74 0.00 16325.75 0.00
8162.87 127.80 8192.67 6502.98 7.81 99.82
sde 0.00 1728.00 0.00 117.80 0.00 14745.60 0.00
7372.80 125.17 8209.36 11227.29 8.49 100.02
sde 0.00 1536.00 0.00 103.80 0.00 13107.20 0.00
6553.60 126.27 8209.10 16729.09 9.64 100.02
sde 0.00 1344.00 0.00 91.60 0.00 11468.80 0.00
5734.40 125.21 8208.69 21481.22 10.92 100.02
sde 0.00 1532.80 0.00 98.00 0.00 13081.60 0.00
6540.80 133.49 8209.34 26583.57 10.21 100.02
sde 0.00 1632.00 0.00 107.00 0.00 13926.40 0.00
6963.20 130.15 8208.89 31662.93 9.35 100.02
sde 0.00 1536.00 0.00 106.40 0.00 13107.20 0.00
6553.60 123.19 8209.66 36443.07 9.40 100.02
sde 0.00 1442.89 0.00 95.59 0.00 12312.63 0.00
6156.31 128.81 8227.23 41446.78 10.49 100.24
sde 0.00 1532.80 0.00 103.00 0.00 13081.60 0.00
6540.80 127.01 8210.77 46606.03 9.71 100.04
sde 0.00 1440.00 0.00 92.00 0.00 12288.00 0.00
6144.00 133.57 8208.82 51421.78 10.87 100.02
sde 0.00 1344.00 0.00 91.80 0.00 11468.80 0.00
5734.40 124.93 8209.86 56524.37 10.90 100.02
sde 0.00 1539.08 0.00 101.00 0.00 13133.47 0.00
6566.73 130.03 8225.59 61477.93 9.92 100.22
sde 0.00 1436.80 0.00 95.40 0.00 12262.40 0.00
6131.20 128.54 8208.88 66566.42 10.48 100.02
sde 0.00 1344.00 0.00 92.40 0.00 11468.80 0.00
5734.40 124.12 8209.47 71466.12 10.82 100.02
sde 0.00 1102.40 0.00 101.00 0.00 9408.38 0.00
4704.19 93.15 8174.36 76538.41 9.88 99.82
sde 0.00 0.00 0.00 89.00 0.00 0.00 0.00 0.00
0.00 7855.72 80795.64 11.24 100.02
sde 0.00 0.00 0.00 91.38 0.00 0.00 0.00 0.00
0.00 7422.53 81823.89 10.97 100.22
sde 0.00 0.00 0.00 96.80 0.00 0.00 0.00 0.00
0.00 6919.07 83194.91 10.33 100.02
sde 0.00 0.00 0.00 91.78 0.00 0.00 0.00 0.00
0.00 6480.85 84657.04 10.92 100.22
sde 0.00 0.00 0.00 92.60 0.00 0.00 0.00 0.00
0.00 5997.22 84749.79 10.80 100.02
sde 0.00 0.00 0.00 91.02 0.00 0.00 0.00 0.00
0.00 5528.97 85345.07 10.97 99.82
sde 0.00 0.00 0.00 102.61 0.00 0.00 0.00
0.00 0.00 5059.61 85057.91 9.77 100.22
sde 0.00 0.00 0.00 93.20 0.00 0.00 0.00 0.00
0.00 4572.57 85284.49 10.73 100.02
sde 0.00 0.00 0.00 98.20 0.00 0.00 0.00 0.00
0.00 4109.15 86086.50 10.21 100.22
sde 0.00 0.00 0.00 91.42 0.00 0.00 0.00 0.00
0.00 3611.72 86405.24 10.92 99.82
sde 0.00 0.00 0.00 100.00 0.00 0.00 0.00
0.00 0.00 3135.62 86292.49 10.00 100.02
sde 0.00 0.00 0.00 100.40 0.00 0.00 0.00
0.00 0.00 2652.63 86609.79 9.96 100.02
sde 0.00 0.00 0.00 92.80 0.00 0.00 0.00 0.00
0.00 2153.69 86168.58 10.78 100.02
sde 0.00 0.00 0.00 88.80 0.00 0.00 0.00 0.00
0.00 1694.74 86275.58 11.26 100.02
sde 0.00 0.00 0.00 98.20 0.00 0.00 0.00 0.00
0.00 1241.41 86708.40 10.19 100.02
sde 0.00 0.00 0.00 95.20 0.00 0.00 0.00 0.00
0.00 747.52 86505.59 10.51 100.02
sde 0.00 0.00 0.00 89.20 0.00 0.00 0.00 0.00
0.00 283.44 86551.11 11.21 100.02
sde 0.00 51.20 0.00 17.20 0.00 449.60 0.00 224.80
26.14 4.30 61572.65 9.05 15.56
sde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00