# RAS Enrollment Server high availability

For high availability, multiple Enrollment Servers (ESs) can be added to each Site. All enabled and verified ESs will be used in an active/active fashion. Upon user login, requests from workload VMs such as RD Session Hosts or VDIs are equally distributed among the available ESs. In case of failures on a particular ES, the next available ES is selected and the SAML SSO authentication process continues. Specifically required for manual deployment of multiple ESs, it is important to note that all ESs in the same site share the same registration key which is required to be deployed in the specified path as mentioned in the [**RAS Enrollment Server configuration**](/landing/ras-admin-guide/parallels-ras-21-administrators-guide/saml-sso-authentication/saml-configuration/ras-enrollment-server-configuration.md) section.

{% hint style="info" %}
**Note:** Multiple ESs do not share a common certificate repository store and all certificates are segregated on each ES. This means that in case of multiple ESs, same user might have different certificates available on different ESs.
{% endhint %}


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