# Modify or add disks

> Every disk on an Azure server includes a host caching mode and a storage type or a storage account

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Which of the two applies depends on the server's existing disks. Servers built with managed disks take a **Storage type** on each new disk; servers built against a storage account take an **Azure Storage Account** instead, and Cloud Management Platform (CMP) creates one if not specified.

## Add a disk

1. Open the server and select the **Disks** tab.
1. Select **Add**.
1. Enter a **Disk Size (GB)** and set **OS Disk Host Caching**.
1. Set **Storage type** or **Azure Storage Account**, whichever the dialog offers.
1. Submit the dialog.

**Add** appears only on an active server in an assigned environment, on a technology that supports adding disks, and only for users with permission to add disks.

## Review, resize, and delete disks

The **Disks** tab shows one card per disk, listing its size, UUID, storage account, host caching, and, where set, the security encryption type.

Each data disk offers resize and delete actions. The OS disk can be resized but not deleted. Both actions need the matching permission, so a disk shows only the actions you can perform.

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Azure allows host caching only on disks of 4095 GB or smaller. On a larger disk, CMP sets caching to `None` and records the change in the job log.
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## Disk parameters

These parameters set the values CMP uses for each disk it creates while provisioning a server. The number in a parameter's name matches the disk size parameter it belongs to, so `disk_1_host_caching` applies to the disk created by **Size for Disk 2**. See [Provisioning](/docs/cmp/configure/infrastructure/resource-handlers/azure/provisioning/) for the disk size parameters.

| Parameter | Name | Description |
| --- | --- | --- |
| **OS Disk Host Caching** | `disk_host_caching` | Caching for the OS disk: `None`, `ReadOnly`, or `ReadWrite`. Defaults to `ReadOnly`. This value is also the fallback for any data disk that does not set its own. |
| **Disk 2 Host Caching**, **Disk 3 Host Caching** | `disk_1_host_caching`, `disk_2_host_caching` | Caching for a data disk, with the same three values. Both ship with CMP. The labels run one ahead of the names because the OS disk is disk 1. |
| **Data disk storage account** | `disk_1_storage_account`, `disk_2_storage_account` | An existing Azure storage account to hold this data disk. Create these parameters yourself; they do not ship with CMP. Unset, the disk follows the server's **Azure Storage Account** (`storage_account_arm`). |
| **Data disk storage type** | `disk_1_storage_account_type`, `disk_2_storage_account_type` | An Azure disk storage type for this data disk, such as `Premium_LRS` or `StandardSSD_LRS`. Create these parameters yourself. Unset, the disk follows the server's **Storage type** (`storage_account_type_arm`). |

## Related

- [Provisioning](/docs/cmp/configure/infrastructure/resource-handlers/azure/provisioning/): the disk size parameters, and the storage type and account a server is built with.
- [Resize VMs](/docs/cmp/configure/infrastructure/resource-handlers/azure/resize-vms/): change a server's size rather than its disks.