This topic introduces different OpenSearch cluster versions, including features supported by each version and its application scenarios. It also describes the characteristics and application scenarios of different cluster security modes (including different application-layer protocols).

Introduction to Different Cluster Versions

When selecting an OpenSearch cluster version, consider factors such as service requirements, available features, performance, security updates, and long-term support, ensuring that the selected version can meet both current and future needs and provide a stable, secure environment for your data.

If you are deploying CSS OpenSearch clusters for the first time, you are advised to use the latest version.
If you are migrating an in-house built or third-party OpenSearch cluster to CSS without altering the cluster, keep the version of the source cluster.
If you are migrating an in-house built or third-party OpenSearch cluster to CSS while recoding it, choose OpenSearch 2.19.0.

**Table 1** Features supported by different versions
Feature	OpenSearch 1.3.6	OpenSearch 2.17.1	OpenSearch 2.19.0	Related Documents
Open-source vector search	√	√	√	k-NN query
CSS vector search	√	x	√	Configuring Vector Search for OpenSearch Clusters
Decoupled storage and compute	√	x	√	Configuring Decoupled Storage and Compute for an OpenSearch Cluster
Switching between hot and cold storage	√	√	√	Switching Between Hot and Cold Storage for an OpenSearch Cluster
Enhanced data ingestion performance	√	x	√	Enhancing the Data Ingestion Performance of OpenSearch Clusters

Cluster Security Modes

Configure the security mode based on the security needs of your cluster.

HTTPS access can be disabled only for OpenSearch 1.3.6 and 2.19.0 security-mode clusters. For other versions, HTTPS access is forcibly enabled and cannot be disabled.

**Table 2** Cluster security modes
Cluster Type	Key Settings	Description	Applicable Scenario
Non-security mode cluster	Security Mode: disabled	Access to such a cluster requires no user authentication, and data will be transmitted in plaintext using HTTP.	Use when creating a cluster for internal testing or workloads that have a low security standard. Advantage: easy to access the cluster. Disadvantage: poor security, as anyone can access the cluster. When the security mode is disabled, public network access and Kibana public network access cannot be enabled. Make sure the cluster is deployed in a secure environment. Do not expose the cluster's network interface to the public network.
Security-mode cluster	Security-mode cluster + HTTP: Security Mode: enabled HTTPS Access: disabled	Such a cluster requires user authentication. It supports access control and data encryption, and it uses HTTP to transmit data in plaintext.	Use to balance security and performance. Advantage: User authentication improves cluster security. HTTP-based access ensures high performance of the cluster. User permissions can be configured to ensure proper isolation. Disadvantage: Public network access is not supported. Make sure the cluster is deployed in a secure environment. Do not expose the cluster's network interface to the public network.
Security-mode cluster	Security-mode cluster + HTTPS: Security Mode: enabled HTTPS Access: enabled	Such a cluster requires user authentication. It supports access control and data encryption, and it uses HTTPS to encrypt communication and enhance data security.	Use when security takes precedence over performance and public network access is required. Advantage: User authentication improves cluster security. HTTPS enhances cluster security by encrypting all communication over the public network. User permissions can be configured to ensure proper isolation. Disadvantage: When HTTPS is used, data encryption and decryption introduce computational overhead and impact the cluster's read and write performance.

To access a security-mode cluster, a username and password need to be provided. CSS supports authentication for the following two types of users:

Administrator: The default administrator username is admin, and the password is the one specified during cluster creation.
Cluster user: created by the cluster administrator on OpenSearch Dashboards. User permissions can be configured to ensure proper isolation. For details, see Creating Users for an OpenSearch Cluster and Granting Cluster Access.

Planning the Cluster Version and Security Mode

Introduction to Different Cluster Versions

Cluster Security Modes