Planning Your SQL Server 2025 Installation

SQL Server 2025 (version 17.x, GA November 2025) introduces significant changes relative to SQL Server 2022 — including native AI capabilities, stricter security defaults, and the removal of several legacy features. A successful installation requires structured planning before the setup wizard ever runs. This lesson walks through the seven planning steps that Microsoft recommends for SQL Server 2025 installations, covering edition selection, hardware requirements, security planning, breaking changes, and post-installation configuration.

Step 1 — Review What Is New, Removed, and Breaking

Before downloading SQL Server 2025 installation media, review the version-specific changes that affect your workload. SQL Server 2025 introduces capabilities that require deliberate adoption and removes features that may be in active use in your current environment.

New and enhanced features in SQL Server 2025:

• AI and vector workloads: Native VECTOR data type, DiskANN-based vector indexing (preview), VECTOR_DISTANCE function, external AI model management, and GitHub Copilot integration in SSMS 22+
• Developer tools: Native REGEXP pattern matching, fuzzy matching (preview), REST endpoint invocation from T-SQL, enhanced JSON functions, and new Chinese collations
• Analytics: Native Parquet, Delta, and CSV file support without requiring PolyBase in many scenarios; PolyBase ODBC support on Linux
• High availability: Always On Availability Groups with async batch dispatching and faster failover; TLS 1.3 support; backups to immutable storage; backup operations on secondary replicas
• Security: TLS 1.3 and TDS 8.0 as the default encryption standard; PBKDF2 password hashing; managed identity support; OAEP padding for encryption operations
• Performance: Optimized locking, tempdb governance, ZSTD compression, Query Store enabled on secondaries by default, and Intelligent Query Processing enhancements

Features removed or discontinued in SQL Server 2025:

• Data Quality Services (DQS) and Master Data Services (MDS) — both removed entirely
• Azure Synapse Link — discontinued
• Built-in Reporting Services — use Power BI Report Server or Microsoft Fabric instead
• Web edition — discontinued; Express with Advanced Services merged into base Express
• Hot-add CPU and lightweight pooling — deprecated

Breaking changes requiring immediate attention:

• TLS 1.3 and TDS 8.0 as defaults break older linked servers, transactional replication, snapshot replication, peer-to-peer replication, merge replication, log shipping, and some PolyBase scenarios. Any environment using these features must be tested thoroughly in a non-production environment before upgrading.
• If upgrading from SQL Server 2022, DQS and MDS must be uninstalled before running SQL Server 2025 setup. Failing to uninstall them causes the installer to fail with a prerequisite error.
• Many AI and vector features require enabling PREVIEW_FEATURES through the database-scoped configuration before they are accessible.

Step 2 — Choose the Right Edition

SQL Server 2025 is available in five editions. Choosing the correct edition before installation prevents costly re-licensing and migration work later:

For students working through this course, the Developer edition is the recommended installation. It provides access to the full SQL Server 2025 Enterprise feature set — including SQL Server Agent, vector workloads, Machine Learning Services, and Always On — without licensing cost, making it ideal for learning all features without artificial limitations.

Step 3 — Verify Hardware, Software, and Storage Requirements

Minimum hardware requirements for all SQL Server 2025 editions:

• Processor: x64 architecture (Intel or AMD), minimum 1.4 GHz, 2.0 GHz or faster recommended, up to 64 cores per NUMA node
• Memory: 512 MB minimum for Express, 1 GB minimum for all other editions. Production deployments should target 4 GB minimum and scale with database size and concurrent connection count.
• Storage: 6 GB free space on the system drive for the installer minimum. A full installation including all features requires approximately 8 GB. The Database Engine components alone require approximately 1.5 GB.
• Display: Super-VGA (800x600) minimum for the installation wizard GUI

Supported operating systems for SQL Server 2025:

• Windows Server 2025, Windows Server 2022, Windows Server 2019 (including Server Core)
• Windows 11 and Windows 10 for Standard and Express editions — not supported for Enterprise production deployment
• .NET Framework 4.7.2 required on all Windows platforms
• Linux: Red Hat Enterprise Linux 8, 9, and 10; Ubuntu 20.04, 22.04, and 24.04; SUSE Linux Enterprise Server — see the Linux installation guide for platform-specific requirements

Storage architecture best practices:

Production SQL Server installations should separate storage across multiple disks or volumes to prevent I/O contention between workloads. The recommended separation is: operating system on one volume; SQL Server data files (.mdf and .ndf) on a second volume; transaction log files (.ldf) on a third volume; tempdb data and log files on a fourth volume; and backup files on a separate volume or network location. SSD or NVMe storage is strongly recommended for data and transaction log volumes in production environments. Run the System Configuration Checker from the SQL Server installation media to verify that the target machine meets all prerequisites before beginning setup.

Step 4 — Plan Security and Service Accounts

Security planning before installation prevents configuration debt that is expensive to correct after SQL Server is in production. Four security decisions must be made before setup begins:

• Authentication mode: Windows Authentication is the recommended and more secure option. Mixed Mode authentication (Windows and SQL Server logins) is required only when applications cannot use Windows Authentication — for example, legacy applications that embed SQL Server credentials in connection strings. If Mixed Mode is selected during installation, the sa account is enabled and must be given a strong password immediately after setup.
• Service accounts: Use group Managed Service Accounts (gMSA) or dedicated low-privilege domain accounts for all SQL Server services. Do not use Local System or Administrator accounts for the Database Engine or SQL Server Agent in production. Do not install SQL Server on a domain controller — the elevated privileges of domain controller accounts create unnecessary security exposure.
• Encryption: SQL Server 2025 defaults to TLS 1.3 and TDS 8.0 for all connections. Plan for Transparent Data Encryption (TDE) for data-at-rest encryption and Always Encrypted for column-level encryption of sensitive data such as personally identifiable information and financial records.
• Firewall and network: TCP port 1433 is the default SQL Server port. Configure Windows Firewall or network firewall rules to allow only authorized client IP ranges to reach this port. For named instances using dynamic ports, SQL Server Browser (UDP port 1434) must also be permitted through the firewall.

Step 5 — Pre-Installation Checklist

Complete the following steps before running the SQL Server 2025 setup wizard:

1. Apply all Windows Server updates and restart the server — SQL Server setup may fail or produce warnings on systems with pending Windows updates
2. Download the SQL Server 2025 installation media from the Microsoft Evaluation Center, Volume Licensing Service Center, or the Microsoft SQL Server download page — the offline installer is recommended for production environments to avoid dependency on internet connectivity during setup
3. If upgrading from SQL Server 2022, uninstall DQS and MDS before running setup to avoid prerequisite failures
4. Back up all existing SQL Server databases, system databases included, if performing an in-place upgrade rather than a new installation
5. Decide on the installation type: standalone instance, SQL Server Failover Cluster Instance (FCI), or Always On Availability Group node
6. Plan the instance name — the default instance is accessed by server name alone; named instances are accessed as servername\instancename and require SQL Server Browser for client discovery
7. Download and install SSMS 22 or Azure Data Studio separately after SQL Server setup completes — neither is included in the SQL Server 2025 installer

Step 6 — Installation and Post-Installation Configuration

The SQL Server 2025 Installation Center wizard guides through component selection, service account configuration, collation selection, authentication mode, and data directory configuration. Select only the features required for your workload — installing unused components increases the attack surface and maintenance overhead without providing value.

Critical post-installation configuration steps:

1. Apply the latest Cumulative Update immediately after installation — SQL Server 2025 cumulative updates are released monthly and include security fixes and bug corrections that may affect production stability
2. Configure max server memory in SSMS to prevent SQL Server from consuming all available RAM and starving the operating system — a common production problem on dedicated SQL Server machines
3. Configure tempdb with multiple data files — one per logical processor up to eight files is the standard recommendation, with all files sized equally to prevent uneven allocation
4. Enable Query Store on all user databases if not already enabled — SQL Server 2025 enables Query Store on secondary replicas by default, but user databases on new standalone instances may require manual enablement
5. Configure Database Mail and SQL Server Agent alerts so that critical error conditions generate notifications before they become outages
6. Enable vector search features for AI workloads by setting PREVIEW_FEATURES = ON at the database scope where vector indexes and VECTOR_DISTANCE queries will be used
7. Verify the SQL Server error log for the startup success message and review any warnings generated during the first service start

Step 7 — High Availability, Containers, and Azure Considerations

High availability and disaster recovery architecture must be planned before installation because some configurations — particularly Always On Availability Groups and Failover Cluster Instances — require specific Windows Server Failover Clustering (WSFC) infrastructure to be in place before SQL Server setup runs.

• Always On Availability Groups provide database-level high availability with automatic failover. SQL Server 2025 Enterprise supports up to eight secondary replicas plus distributed availability groups spanning multiple WSFC clusters. Standard edition supports basic availability groups with one secondary replica and manual failover.
• Failover Cluster Instances provide instance-level high availability through shared storage. The entire SQL Server instance fails over to a surviving cluster node when the primary node fails — all databases on the instance fail over together.
• Containers: SQL Server 2025 container images are available on Microsoft Container Registry and support Docker and Kubernetes deployments. Container-based installations use environment variables for configuration rather than the setup wizard — plan connection strings, service accounts, and persistent storage volumes before deploying SQL Server in containers.
• Azure Arc: Enrolling on-premises SQL Server 2025 instances in Azure Arc enables unified management through the Azure portal, automated patching, Microsoft Defender for SQL, and pay-as-you-go billing options. Azure Arc enrollment requires outbound internet connectivity from the SQL Server machine to Azure Arc endpoints.

Summary

Planning a SQL Server 2025 installation requires working through seven structured steps before the setup wizard runs: reviewing breaking changes and removed features, selecting the correct edition for the workload, verifying hardware and OS requirements, planning service accounts and encryption, completing the pre-installation checklist, configuring the instance after setup, and designing the high availability architecture. SQL Server 2025 Developer edition is the recommended installation for students and developers — it provides the full Enterprise feature set including vector workloads, Machine Learning Services, and Always On at no cost for non-production use. The breaking change most likely to affect existing environments is the TLS 1.3 and TDS 8.0 default — any linked servers, replication topologies, or log shipping configurations must be tested against SQL Server 2025 before upgrading production instances. The next lesson covers the SQL Server 2025 architecture in detail.