# Upgrade or repair an Aerospike server

Aerospike supports cluster upgrades without service downtime or data loss through a rolling upgrade. In a rolling upgrade, you stop one server node at a time, upgrade it, and restart it, as described below. During this process, the database cluster continues to serve traffic and experiences no loss of data availability.

You can use a rolling upgrade to:

-   [Upgrade Aerospike Database](https://aerospike.com/docs/database/install/upgrade/standard) from one version to another.
-   [Upgrade hardware](https://aerospike.com/docs/database/install/upgrade/hardware) or replace failed hardware.

::: caution
See [Special upgrades and downgrades](https://aerospike.com/docs/database/advanced/special-upgrades) for important upgrade information relevant to specific versions.
:::

Before upgrading, review the [release notes](https://aerospike.com/docs/database/release) for the targeted version to learn about important changes and any special considerations you should be aware of.

## Estimating the time required for an upgrade

Aerospike Database handles large volumes of data, and the time it takes each node to restart and rebalance data across the cluster will vary. Therefore, it is difficult to estimate the time an upgrade will take.

::: note
-   If your configuration allows for a [fast restart](https://aerospike.com/docs/database/manage/database/fast-start), the server restart typically only takes a few minutes. For example, if you want to upgrade the Aerospike Database version on your cluster, it should only take a few minutes to take down a server, install the new version, and restart.
-   To install a new SSD, see [How to add, replace and remove disks](https://support.aerospike.com/s/article/How-to-add-replace-and-remove-disks) for more information.
-   The longer a server is down, the longer the rebalancing process (migration) will take.
-   You cannot ship XDR records with compression enabled from Aerospike Database 4.8.0 or later to Aerospike Database 4.3.1 or earlier. See [Special upgrade from Database 4.3.0 to 4.9](https://aerospike.com/docs/database/advanced/special-upgrades/430-to-490-upgrade) for more information.
:::