How to calculate your EBS volume IOPS on CloudWatch

By Rackspace Technical Staff

Originally published in Apr 2017, at the Onica blog here.

What is EBS used for?

Our Managed Services team works with clients who often inquire about the performance of their EBS volumes, which are crucial for production servers. By better understanding how to monitor your EBS volumes, your IT team can prevent slowness and latencies, which would impact your end-users and the company’s operations. Also, it helps you scale to the right IOPS level to optimize cost within your business as well as upgrade your infrastructure levels.

EBS provides highly available, raw block-level storage volumes that can be attached to Amazon Elastic Compute Cloud; (EC2) instances and is used by Amazon Relational Database Service;(RDS).EBS enables you to keep data persistently on a file system, even after you shut down your EC2 instance.

What is an IOPS AWS?

IOPS is a popular performance metric used to distinguish one storage type from another. Similar to device makers, AWS associates IOPS values with the volume component backing the storage option. Provisioned IOPS is an EBS volume type designed to deliver predictable, high-level performance for I/O-intensive workloads such as database applications.

Using the CloudWatch dashboard to calculate Your EBS Volume IOPS

Whereas you can easily view RDS and EC2 instances’ IOPS metrics through AWS graphs, getting the same insight on the CloudWatch dashboard requires you to run some calculations to find the IOPS used in a specific period.

You can calculate the IOPS usage simply by dividing the total read and write throughputs (ops) of your disk by the time in seconds within that period.

    IOPS Usage = (Total Read + Write Throughputs) / Time (in Seconds)

This article explains how to do that calculation on AWS. Use it to determine if your EBS volumes require more IOPS to be provisioned or if they just need to be initialized or pre-warmed, which is the case for recently launched volumes from S3 snapshots that normally cause spikes in the Average Queue Length despite normal IOPS metrics.


For this example, we used a SQL database instance where the SQL operations run on D: drive, /dev/sdb our device code on AWS.

1. You can find the EBS device code on the bottom right of the instance properties. Use this link to get more information on how to map the EBS Devices to match your local volume Drive Letter.

IOPS Pic 1

2. After you click on the volume code, you see the EBS Volume ID, which you should copy. Next, open CloudWatch, and click Metrics on the bottom left. 

IOPS Pic 2

3. Choose All > EBS > Per-Volume Metrics

4. Select the desired metric volume, either VolumeWriteOps (write throughput) or VolumeReadOps (read throughput).

IOPS Pic 3

In this case, choose VolumeReadOps and then choose a specific time and the data-point period. In this scenario, I chose to monitor or zoom the dataset at 08:15 (UTC) with a data-point period of 15 minutes because I observed spikes that started close to 8:00 AM and ended around 8:30 AM. Our goal is to find the IOPS utilized within those 15 minutes. 

IOPS Pic 4

5. Make sure you change your Metric Statistic to SUM from AVERAGE and find your VolumeReadOps sum between 08:00 – 08:15

IOPS Pic 5

 6. Then, find your VolumeWriteOps sum between 8:00 – 8:15:

IOPS Pic 6

The calculation 

Now that we have both Read and Write Throughput sums for the closest data point to 08:15 UTC, we are ready to calculate the IOPS.

Note: By choosing one minute, we could have gotten more precise numbers within a minute. However, if there are no major disk Ops spikes within those 15 minutes, it should suffice.

Remember the formula we presented in the beginning?


In our example:

    VolumeReadOps is 3,027,754 + VolumeWriteOps is 12,587) / (60 seconds x 15 minutes)

    = 3,040,341/ 900

    = 3,378 Total IOPS

From this point, you can compare your total IOPS provisioned for that volume to prevent latencies for your server. On default settings, the number of IOPS provisioned is three times the EBS volume size based on the I/O Credit Balance you receive for a General Purpose SSD (GP2) from AWS.  You can increase this up to 10,000 IOPS or convert it to a PIOPS EBS Volume Type to receive a higher amount if needed.

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