> For the complete documentation index, see [llms.txt](https://docs.north.cloud/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.north.cloud/docs/features/rightsize/ebs.md).

# EBS

Learn how Rightsize finds savings on EBS volumes.

On AWS accounts, Rightsize identifies EBS volumes that cost more than their usage requires. It recommends a cheaper volume type, lower provisioned IOPS (input/output operations per second) or throughput, or a review of a volume that shows no activity.

## What Rightsize Recommends

Rightsize checks each volume in this order, and the first match sets the recommendation:

* **Review an idle volume for deletion** - a gp3 volume that you pay extra performance for shows no read or write activity. The saving is the volume's whole monthly cost.
* **Change to a cheaper volume type** - a cheaper volume type is available at the same capacity.
* **Lower provisioned IOPS or throughput** - you pay for more IOPS or throughput on a gp3 volume than its traffic needs.

EBS checks are fixed rules. Unlike EC2, they have no sizing target and no per-service settings. The account-wide settings in EBS Settings, below, still apply. Each rule is described below.

## How Rightsize Checks a Volume

Rightsize reads CloudWatch metrics only for gp3 volumes that you pay extra IOPS or throughput for. For those volumes, it reads read and write operations, and read and write bytes, over the lookback window. It reads each one two ways: the total for each period, and the highest single sample in each period. A cheaper volume type does not depend on these metrics, so Rightsize can recommend one for any volume.

### Idle Volumes

Rightsize treats one of these gp3 volumes as idle when every one of its metrics comes back empty across at least 10 days in which the volume was billed. AWS sends EBS metrics to CloudWatch only while a volume is attached to an instance, so empty metrics usually mean that the volume is not attached. In such cases, Rightsize states **Review before deleting** and **Idle** as its findings.

### Cheaper Volume Types

Rightsize recommends gp3 for gp2 volumes of up to 1,000 GiB, because a larger gp2 volume has a higher IOPS baseline than gp3. Rightsize can also recommend gp3 for io1 volumes. It does not recommend a change for io2 volumes. In such cases, Rightsize states **Cheaper volume type available** as its finding.

### Provisioned IOPS and Throughput

On a gp3 volume, you pay extra for IOPS above 3,000 and for throughput above 125 MiB/s. Rightsize checks each of the two separately. It recommends lowering a value to its baseline when the volume's highest traffic, plus 25% headroom, fits within that baseline:

```
trim allowed when (peak read + peak write) × 1.25 ≤ baseline
```

Peak read and peak write are the highest single samples in the lookback window. Rightsize adds them together even when they occurred at different times, so the sum can only overstate the true peak.

For example, take a gp3 volume provisioned with 6,000 IOPS, a peak of 1,400 read IOPS, and a peak of 900 write IOPS:

```
(1,400 + 900) × 1.25 = 2,875 ≤ 3,000
```

The result fits within the baseline, so Rightsize recommends lowering the volume to 3,000 IOPS. The saving is the monthly cost of the provisioned IOPS above the baseline. In such cases, Rightsize states **Volume IOPS Overprovisioned** or **Volume Throughput Overprovisioned** as its finding.

Rightsize lowers a value only to the baseline, never to a point in between. When read or write data is missing, Rightsize does not recommend lowering that value.

## Using the EBS Tab

The summary metrics on the EBS tab are Available Savings, Idle, Optimized, Not Optimized, Tagged, and Untagged.

Click a row's **AI Suggestion** button to open the volume's panel:

* **Current State** - the volume's name and type, and its size, IOPS, and throughput when Rightsize has them.
* **Noros Recommendation** - the values that change, such as the new volume type or IOPS.
* **Monthly Savings** - the estimated saving.
* **Findings** - the reasons behind the recommendation, as chips.

Below the panel sections, a chart shows the volume's read and write IOPS and throughput.

## EBS Settings

EBS has no per-service override settings. These account-wide settings apply to EBS volumes:

* **Metric lookback** and **Min savings**, under **Advanced**.
* **Spend coverage**, **Cost change threshold**, and **Max result age**, under **Advanced**.
* **Analysis cost floor** and **Monthly metrics budget**, under **Spend guardrail**.

**CPU percentile**, **CPU headroom**, **Memory headroom**, and **Min savings percent** do not apply to EBS volumes.

## EBS Finding Reasons

Rightsize lists the reasons behind each finding. Check these before you act on a recommendation, to understand what it is based on.

| Reason                                | Meaning                                                                                                                                               |
| ------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Volume IOPS Overprovisioned**       | You pay for provisioned IOPS that an active volume does not use.                                                                                      |
| **Volume Throughput Overprovisioned** | You pay for provisioned throughput that an active volume does not use.                                                                                |
| **Cheaper volume type available**     | A cheaper volume type offers the same capacity.                                                                                                       |
| **Burst capacity verified**           | This reason appears with every IOPS or throughput reduction. The volume's peak read and write traffic, plus 25%, fits within the baseline.            |
| **Review before deleting**            | Rightsize recommends removing this volume.                                                                                                            |
| **Idle**                              | The volume shows no meaningful read or write activity.                                                                                                |
| **No observed activity**              | All of the volume's metrics came back empty, but over too few billed days to count as idle. Rightsize does not lower the volume's IOPS or throughput. |


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