Re: Load distributed checkpoint - Mailing list pgsql-hackers

From: "Bruce Momjian" <bruce@momjian.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