All of our Kafka clusters are fairly write-heavy. The cluster in question is our second-heaviest – we haven’t yet upgraded the heaviest, due to the issues we’ve been experiencing in this one.
Here is an iostat example from a host within the same cluster, but without the RAID check running:
[root@r2k1 ~] # iostat -xdmc 1 10
Linux 3.10.0-327.13.1.el7.x86_64 (r2k1) 05/27/16 _x86_64_ (32 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
8.87 0.02 1.28 0.21 0.00 89.62
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.02 0.55 0.15 27.06 0.03 11.40 859.89 1.02 37.40 36.13 37.41 6.86 18.65
sdf 0.02 0.48 0.15 26.99 0.03 11.40 862.17 0.15 5.56 40.94 5.37 7.27 19.73
sdk 0.03 0.58 0.22 27.10 0.03 11.40 857.01 1.60 58.49 36.20 58.67 7.17 19.58
sdb 0.02 0.52 0.15 27.43 0.03 11.40 848.37 0.02 0.78 42.84 0.55 7.07 19.50
sdj 0.02 0.55 0.15 27.11 0.03 11.40 858.28 0.62 22.70 41.97 22.59 7.43 20.27
sdg 0.03 0.68 0.22 27.76 0.03 11.40 836.98 0.76 27.10 34.36 27.04 7.33 20.51
sde 0.03 0.48 0.22 26.99 0.03 11.40 860.43 0.33 12.07 33.16 11.90 7.34 19.98
sda 0.03 0.52 0.22 27.43 0.03 11.40 846.65 0.57 20.48 36.42 20.35 7.34 20.31
sdh 0.02 0.68 0.15 27.76 0.03 11.40 838.63 0.47 16.66 40.96 16.53 7.20 20.09
sdc 0.03 0.55 0.22 27.06 0.03 11.40 858.19 0.74 27.30 36.96 27.22 7.55 20.58
sdi 0.03 0.53 0.22 27.13 0.03 11.40 856.04 1.60 58.50 27.43 58.75 5.21 14.24
sdl 0.02 0.56 0.15 27.11 0.03 11.40 858.27 1.12 41.09 27.89 41.16 5.00 13.63
md127 0.00 0.00 2.53 161.84 0.36 68.39 856.56 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
13.11 0.00 1.82 1.07 0.00 84.01
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.00 0.00 0.00 81.00 0.00 38.48 972.95 51.00 219.06 0.00 219.06 6.37 51.60
sdf 0.00 1.00 0.00 73.00 0.00 33.70 945.33 55.02 235.86 0.00 235.86 7.12 52.00
sdk 0.00 1.00 0.00 56.00 0.00 25.70 939.73 60.45 223.79 0.00 223.79 9.29 52.00
sdb 0.00 2.00 0.00 70.00 0.00 34.48 1008.70 58.88 292.81 0.00 292.81 7.37 51.60
sdj 0.00 3.00 0.00 62.00 0.00 29.87 986.60 59.32 243.48 0.00 243.48 8.26 51.20
sdg 0.00 1.00 0.00 49.00 0.00 23.43 979.45 60.37 234.98 0.00 234.98 10.53 51.60
sde 0.00 1.00 0.00 61.00 0.00 27.95 938.38 58.17 239.57 0.00 239.57 8.52 52.00
sda 0.00 2.00 0.00 56.00 0.00 27.48 1004.88 56.27 202.88 0.00 202.88 9.27 51.90
sdh 0.00 1.00 0.00 70.00 0.00 33.57 982.19 59.00 277.84 0.00 277.84 7.43 52.00
sdc 0.00 0.00 0.00 64.00 0.00 30.06 961.89 58.20 268.30 0.00 268.30 8.08 51.70
sdi 0.00 3.00 0.00 116.00 0.00 55.62 981.94 44.54 199.72 0.00 199.72 4.56 52.90
sdl 0.00 1.00 0.00 128.00 0.00 60.31 964.88 43.91 215.94 0.00 215.94 4.11 52.60
md127 0.00 0.00 0.00 1143.00 0.00 538.90 965.59 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
15.70 0.00 1.97 0.44 0.00 81.89
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.00 0.00 0.00 119.00 0.00 56.39 970.42 42.84 639.45 0.00 639.45 6.66 79.20
sdf 0.00 1.00 0.00 129.00 0.00 61.21 971.84 48.89 672.04 0.00 672.04 6.34 81.80
sdk 0.00 0.00 0.00 152.00 0.00 72.62 978.53 61.02 716.76 0.00 716.76 5.74 87.20
sdb 0.00 1.00 0.00 133.00 0.00 62.86 967.88 54.10 695.35 0.00 695.35 6.45 85.80
sdj 0.00 0.00 0.00 146.00 0.00 68.36 958.85 69.22 767.12 0.00 767.12 6.85 100.00
sdg 0.00 0.00 0.00 146.00 0.00 69.87 980.11 77.99 789.53 0.00 789.53 6.85 100.00
sde 0.00 1.00 0.00 141.00 0.00 66.96 972.60 56.21 707.61 0.00 707.61 6.21 87.60
sda 0.00 1.00 0.00 147.00 0.00 69.86 973.22 62.21 728.76 0.00 728.76 6.32 92.90
sdh 0.00 0.00 0.00 134.00 0.00 62.61 956.90 55.79 711.49 0.00 711.49 6.63 88.90
sdc 0.00 0.00 0.00 136.00 0.00 64.81 975.94 61.46 753.57 0.00 753.57 6.93 94.20
sdi 0.00 0.00 0.00 93.00 0.00 42.67 939.61 17.60 419.10 0.00 419.10 4.63 43.10
sdl 0.00 0.00 0.00 80.00 0.00 38.02 973.20 11.00 340.79 0.00 340.79 4.25 34.00
md127 0.00 0.00 0.00 87.00 0.00 40.99 964.97 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
12.11 0.00 1.35 0.00 0.00 86.54
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 15.00 0.00 15.00 15.00 1.50
sdf 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 11.00 0.00 11.00 11.00 1.10
sdk 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 11.00 0.00 11.00 11.00 1.10
sdb 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 7.00 0.00 7.00 7.00 0.70
sdj 0.00 0.00 0.00 2.00 0.00 0.06 64.50 0.01 733.50 0.00 733.50 7.50 1.50
sdg 0.00 0.00 0.00 10.00 0.00 2.88 588.90 0.55 1212.80 0.00 1212.80 15.50 15.50
sde 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 12.00 0.00 12.00 12.00 1.20
sda 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 11.00 0.00 11.00 11.00 1.10
sdh 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.02 20.00 0.00 20.00 20.00 2.00
sdc 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.02 17.00 0.00 17.00 17.00 1.70
sdi 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.01 12.00 0.00 12.00 12.00 1.20
sdl 0.00 0.00 0.00 1.00 0.00 0.00 1.00 0.02 17.00 0.00 17.00 17.00 1.70
md127 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
avg-cpu: %user %nice %system %iowait %steal %idle
15.22 0.00 1.50 0.00 0.00 83.28
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 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
sdf 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
sdk 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
sdb 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
sdj 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
sdg 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
sda 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
sdh 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
sdc 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
sdi 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
sdl 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
md127 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
avg-cpu: %user %nice %system %iowait %steal %idle
16.96 0.09 1.63 0.16 0.00 81.16
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.00 0.00 0.00 8.00 0.00 0.66 168.25 0.09 11.50 0.00 11.50 8.75 7.00
sdf 0.00 0.00 0.00 5.00 0.00 0.52 213.20 0.08 16.20 0.00 16.20 16.20 8.10
sdk 0.00 0.00 0.00 3.00 0.00 0.50 342.00 0.06 20.33 0.00 20.33 20.33 6.10
sdb 0.00 0.00 0.00 3.00 0.00 0.50 342.00 0.05 16.67 0.00 16.67 16.67 5.00
sdj 0.00 0.00 0.00 4.00 0.00 0.98 500.50 0.06 14.50 0.00 14.50 11.00 4.40
sdg 0.00 1.00 0.00 4.00 0.00 0.63 322.50 0.14 36.00 0.00 36.00 32.75 13.10
sde 0.00 0.00 0.00 5.00 0.00 0.52 213.20 0.07 13.60 0.00 13.60 13.60 6.80
sda 0.00 0.00 0.00 3.00 0.00 0.50 342.00 0.05 15.67 0.00 15.67 15.67 4.70
sdh 0.00 1.00 0.00 4.00 0.00 0.63 322.50 0.06 14.50 0.00 14.50 11.50 4.60
sdc 0.00 0.00 0.00 8.00 0.00 0.66 168.25 0.11 13.25 0.00 13.25 10.62 8.50
sdi 0.00 0.00 0.00 4.00 0.00 0.98 500.50 0.06 15.50 0.00 15.50 12.00 4.80
sdl 0.00 0.00 0.00 3.00 0.00 0.50 342.00 0.04 13.67 0.00 13.67 13.67 4.10
md127 0.00 0.00 0.00 17.00 0.00 3.78 455.53 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
14.08 0.00 1.50 0.00 0.00 84.42
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 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
sdf 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
sdk 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
sdb 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
sdj 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
sdg 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
sda 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
sdh 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
sdc 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
sdi 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
sdl 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
md127 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
avg-cpu: %user %nice %system %iowait %steal %idle
14.89 0.00 1.98 0.00 0.00 83.13
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.00 0.00 0.00 90.00 0.00 41.31 940.01 27.25 302.80 0.00 302.80 7.07 63.60
sdf 0.00 0.00 0.00 87.00 0.00 41.35 973.44 22.73 261.30 0.00 261.30 6.92 60.20
sdk 0.00 2.00 0.00 97.00 0.00 42.08 888.42 39.86 410.94 0.00 410.94 8.10 78.60
sdb 0.00 0.00 0.00 87.00 0.00 41.07 966.82 24.39 280.30 0.00 280.30 7.14 62.10
sdj 0.00 1.00 0.00 91.00 0.00 41.94 943.92 36.37 399.62 0.00 399.62 8.44 76.80
sdg 0.00 0.00 0.00 86.00 0.00 40.67 968.48 31.76 369.33 0.00 369.33 8.81 75.80
sde 0.00 0.00 0.00 87.00 0.00 41.35 973.44 30.80 354.05 0.00 354.05 9.01 78.40
sda 0.00 0.00 0.00 87.00 0.00 41.07 966.82 32.61 374.80 0.00 374.80 8.57 74.60
sdh 0.00 0.00 0.00 86.00 0.00 40.67 968.48 29.52 343.23 0.00 343.23 8.56 73.60
sdc 0.00 0.00 0.00 89.00 0.00 40.81 939.07 32.80 360.15 0.00 360.15 8.91 79.30
sdi 0.00 1.00 0.00 91.00 0.00 41.94 943.92 19.60 215.34 0.00 215.34 5.62 51.10
sdl 0.00 2.00 0.00 97.00 0.00 42.08 888.42 19.59 201.93 0.00 201.93 4.69 45.50
md127 0.00 0.00 0.00 535.00 0.00 248.42 950.95 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
11.08 0.00 1.41 0.00 0.00 87.51
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 0.00 5.00 0.00 42.00 0.00 0.38 18.55 2.25 53.52 0.00 53.52 4.93 20.70
sdf 0.00 0.00 0.00 35.00 0.00 0.21 12.43 1.62 46.17 0.00 46.17 5.29 18.50
sdk 0.00 23.00 0.00 42.00 0.00 0.44 21.40 1.99 47.29 0.00 47.29 4.64 19.50
sdb 0.00 9.00 0.00 58.00 0.00 0.34 12.02 2.77 47.78 0.00 47.78 4.12 23.90
sdj 0.00 1.00 0.00 39.00 0.00 0.24 12.79 1.79 45.97 0.00 45.97 5.21 20.30
sdg 0.00 11.00 0.00 66.00 0.00 0.40 12.45 3.60 54.47 0.00 54.47 3.42 22.60
sde 0.00 0.00 0.00 35.00 0.00 0.21 12.43 2.13 61.00 0.00 61.00 8.89 31.10
sda 0.00 9.00 0.00 58.00 0.00 0.34 12.02 2.48 42.81 0.00 42.81 3.71 21.50
sdh 0.00 11.00 0.00 66.00 0.00 0.40 12.45 4.81 72.83 0.00 72.83 3.80 25.10
sdc 0.00 5.00 0.00 43.00 0.00 0.88 41.93 1.99 63.81 0.00 63.81 5.00 21.50
sdi 0.00 1.00 0.00 39.00 0.00 0.24 12.79 1.31 33.69 0.00 33.69 4.03 15.70
sdl 0.00 23.00 0.00 42.00 0.00 0.44 21.40 1.23 29.33 0.00 29.33 3.71 15.60
md127 0.00 0.00 0.00 313.00 0.00 2.01 13.14 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
16.16 0.03 1.66 0.00 0.00 82.15
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 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
sdf 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
sdk 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
sdb 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
sdj 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
sdg 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
sda 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
sdh 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
sdc 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
sdi 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
sdl 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
md127 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
On 2016-05-26, 11:50 PM, "centos-bounces@xxxxxxxxxx on behalf of Gordon Messmer" <centos-bounces@xxxxxxxxxx on behalf of gordon.messmer@xxxxxxxxx> wrote:
>On 05/25/2016 09:54 AM, Kelly Lesperance wrote:
>> What we're seeing is that when the weekly raid-check script executes, performance nose dives, and I/O wait skyrockets. The raid check starts out fairly fast (20000K/sec - the limit that's been set), but then quickly drops down to about 4000K/Sec. dev.raid.speed sysctls are at the defaults:
>
>It looks like some pretty heavy writes are going on at the time. I'm not
>sure what you mean by "nose dives", but I'd expect *some* performance
>impact of running a read-intensive process like a RAID check at the same
>time you're running a write-intensive process.
>
>Do the same write-heavy processes run on the other clusters, where you
>aren't seeing performance issues?
>
>> avg-cpu: %user %nice %system %iowait %steal %idle
>> 9.24 0.00 1.32 20.02 0.00 69.42
>>
>> Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
>> sda 50.00 512.00 20408.00 512 20408
>> sdb 50.00 512.00 20408.00 512 20408
>> sdc 48.00 512.00 19984.00 512 19984
>> sdd 48.00 512.00 19984.00 512 19984
>> sdf 50.00 704.00 19968.00 704 19968
>> sdg 47.00 512.00 19968.00 512 19968
>> sdh 47.00 512.00 19968.00 512 19968
>> sde 50.00 704.00 19968.00 704 19968
>> sdj 48.00 512.00 19972.00 512 19972
>> sdi 48.00 512.00 19972.00 512 19972
>> sdk 48.00 512.00 19980.00 512 19980
>> sdl 48.00 512.00 19980.00 512 19980
>> md127 241.00 0.00 120280.00 0 120280
>
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