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I have a running Mysql db.m3.medium RDS instance at AWS, running with 20GB SSD as in: RDS machine description

Last hour write and read operations went as following: Disk operations

It looks like max(write)+max(read) operations total around 50/second, which means it is under the 3 * disk_capacity = 3 * 20 = 60 iops/second. So it means that every second I am getting extra 10 iops in my credit balance.

With this in mind, my current credit count is the credit count before this time period (1 hour) + sum(credit balance for each second time frame)?

Is this the correct way of calculating current IOPS usage and credit accumulation/count?

If so, there is no AWS graph that displays IOPS credit usage, as there is a CPU credit usage, correct?

Guilherme Silveira
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5 Answers5

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As mentioned in How can I see my IOPS burst credits? (source):

Unfortunately there isn't a Cloudwatch Metric for the current IOPS Credit balance like there is with the CPU credits.

This has still not been implemented as of July 2016.

The AWS docs offer a pretty good introduction to IOPS burst:

Each volume receives an initial I/O credit balance of 5.4 million I/O credits, which is enough to sustain the maximum burst performance of 3,000 IOPS for 30 minutes. This initial credit balance is designed to provide a fast initial boot cycle for boot volumes and to provide a good bootstrapping experience for other applications. Volumes earn I/O credits at the baseline performance rate of 3 IOPS per GiB of volume size. For example, a 100 GiB gp2 volume has a baseline performance of 300 IOPS.

When your volume requires more than the baseline performance I/O level, it draws on I/O credits in the credit balance to burst to the required performance level, up to a maximum of 3,000 IOPS. Volumes larger than 1,000 GiB have a baseline performance that is equal or greater than the maximum burst performance, and their I/O credit balance never depletes. When your volume uses fewer I/O credits than it earns in a second, unused I/O credits are added to the I/O credit balance. The maximum I/O credit balance for a volume is equal to the initial credit balance (5.4 million I/O credits).

So taking your example, your 20 GB volume has a baseline performance of 60 IOPS. If you use an average of 50 IOPS, 10 I/O credits will be added to your credit balance every second, up to a maximum of 5.4 million I/O credits.

Community
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BenMorel
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  • While the way IOPS work might be the same, your linked documents are all about EBS IOPS, not RDS IOPS. Meanwhile EBS IOPS credits can be monitored via Cloudwatch, but RDS not. – einSelbst Jun 20 '17 at 11:02
  • See also: @Salami's [comment](https://serverfault.com/q/653340/148275): "You can a tleast know that you are running out of credits by looking at the queue depth stat. Queue depth is "the number of I/O requests in the queue waiting to be serviced." – Efren Mar 07 '18 at 02:19
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AWS just released the feature, this may help you to monitor your IOPS:

Burst Bucket Metric Now Available for Amazon EBS General Purpose SSD (gp2) Volumes

(at the moment it's only available for gp2 volumes, but we can guess other volumes are on the way)

Sebastien Horin
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Although burst balance graph is not yet available in web console it can be retrieved in aws cli with command like this:

aws cloudwatch get-metric-statistics --namespace AWS/RDS --metric-name  BurstBalance --dimensions Name=DBInstanceIdentifier,Value=YOUR_INSTANCE_NAME --start-time $(date +%s -d "-6 hours") --end-time $(date +%s) --period 30 --statistics Average

This command will return something like this:

DATAPOINTS      99.999962963    2018-12-26T18:00:00Z    Percent
DATAPOINTS      100.0   2018-12-26T17:25:00Z    Percent
DATAPOINTS      99.999962963    2018-12-26T16:50:00Z    Percent
DATAPOINTS      100.0   2018-12-26T16:15:00Z    Percent
Vladimir
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Building on the answer of Vladimir: the BurstBalance metric is now also available in Cloudwatch, so you can set up and alarm based on it there.

severin
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This is available for EC2 gp2 Volumes as well as RDS gp2 Volumes.

To view it for EC2 EBS Volumes, go to Cloudwatch -> Metrics -> EBS -> BurstBalance.

To view it for RDS Instances, go to Cloudwatch -> Metrics -> RDS -> BurstBalance.

Jay Jayswal
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