The performance of a site is impacted by the amount of reads and writes that occur for disk volumes. The primary volume that can be impacted is the database volume, if there are a large number of queries that are running against the volume. For this kind of scenario, having a high amount of Input/Output Operations Per Second (IOPS) can cause rate limiting to occur where the amount of IOPS is restricted to a maximum value. For more details on Input/Output Operations Per Second (IOPS) being rate limited, see the article, My site is slow with slow running queries.
To check if the database volume has a high number of IOPS and that it maybe tending towards a rate limited event you can use the iostat command, which displays the CPU statistics and input/output statistics for devices and partitions.
This command can be used to check on the state of the IOPs by checking the %util column. If this column shows consistently over 95% then the volume is saturated.
An example of the command to use is:
iostat -x -h <delay_in_seconds> <frequency> <volume>Where the options and parameters are:
-x - Display extended statistics.-h - Make the Device Utilization Report easier to read by a human.<delay_in_seconds> - is the delay time in seconds in which to run the check on statistics.<frequency> - the amount of times to run the check on statistics.<volume> - volume name to check against.
For further details on the command use man iostat.
An example of running the command is :
iostat -x -h 1 10 /dev/nvme4n1A summary of these parameters are :
1 - is the delay time in seconds in which to run the check on statistics - in this case every 1 second.10 - the amount of times to run the check on statistics - in this case, check on statistics 10 times./dev/nvme4n1 - volume name to check against - in this case the database volume - /vol/ebs1
Running that command against the volume :
$ iostat -x -h 1 10 /dev/nvme4n1
Linux 4.4.0-1101-aws (ded-32426.prod.hosting.acquia.com) 06/19/2020 _x86_64_ (4 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
3.14 0.00 1.31 1.65 0.00 93.90
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.11 0.32 105.53 1.54 601.34 11.39 0.21 1.95 2.56 1.95 1.33 14.03
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 0.00 0.25 0.00 99.75
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 19.00 0.00 87.00 9.16 0.01 0.42 0.00 0.42 0.42 0.80
avg-cpu: %user %nice %system %iowait %steal %idle
0.75 0.00 0.00 0.00 0.00 99.25
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 24.00 0.00 237.00 19.75 0.02 1.00 0.00 1.00 1.00 2.40
avg-cpu: %user %nice %system %iowait %steal %idle
2.25 0.00 2.25 0.00 0.00 95.50
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 32.00 0.00 297.00 18.56 0.01 0.38 0.00 0.38 0.38 1.20
avg-cpu: %user %nice %system %iowait %steal %idle
0.50 0.00 0.00 0.25 0.00 99.25
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 18.00 0.00 131.00 14.56 0.00 0.22 0.00 0.22 0.22 0.40
avg-cpu: %user %nice %system %iowait %steal %idle
0.25 0.00 0.25 0.00 0.00 99.50
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 21.00 0.00 137.00 13.05 0.02 0.95 0.00 0.95 0.76 1.60
avg-cpu: %user %nice %system %iowait %steal %idle
0.25 0.00 0.00 0.25 0.00 99.50
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 22.00 0.00 120.50 10.95 0.01 0.36 0.00 0.36 0.36 0.80
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 0.00 0.00 0.00 100.00
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 20.00 0.00 199.00 19.90 0.01 0.40 0.00 0.40 0.40 0.80
avg-cpu: %user %nice %system %iowait %steal %idle
1.00 0.00 0.00 0.00 0.00 99.00
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 28.00 0.00 361.00 25.79 0.01 0.43 0.00 0.43 0.29 0.80
avg-cpu: %user %nice %system %iowait %steal %idle
0.50 0.00 0.00 0.00 0.00 99.50
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme4n1
0.00 0.00 0.00 47.00 0.00 589.00 25.06 0.02 0.34 0.00 0.34 0.34 1.60If this content did not answer your questions, try searching or contacting our support team for further assistance.
Wed Oct 22 2025 08:59:29 GMT+0000 (Coordinated Universal Time)