Installing and configuring SQL Server 2025 on Windows Server

Prerequisites

Minimum and recommended hardware

Software requirements

Note: SQL Server 2025 installs on x64 processors only. 32-bit installations are no longer supported.

Storage good practice before installing

Separate your files physically to optimize I/O:

Data files are accessed randomly, whereas transaction logs are accessed sequentially. Separating them reduces contention on the heads of mechanical disks and improves performance significantly.

Editions available in SQL Server 2025

SQL Server 2025 introduces one key new edition: Standard Developer.

Why Standard Developer matters: teams used to run the Developer edition, equivalent to Enterprise, in dev and test, then Standard in production. That produced behavioural differences — Batch Mode on Rowstore and Online Index Rebuild are absent from Standard, for instance. Standard Developer removes the problem by guaranteeing feature parity across every environment.

What is new in SQL Server 2025

Before starting the installation, here are the features that justify the upgrade:

• the VECTOR data type and the VECTOR_DISTANCE function for semantic search (cosine, Euclidean, dot product);
• DiskANN vector indexes (CREATE VECTOR INDEX) for large-scale ANN search, in preview;
• native AI integration: Azure OpenAI, LangChain, Semantic Kernel, Entity Framework Core;
• improved native JSON support, with JSON indexes;
• Change Event Streaming and a built-in REST API;
• improved optimized locking, to reduce contention;
• extended Intelligent Query Processing;
• Microsoft Fabric integration for hybrid analytics.

Downloading the installation media

1. Go to the official page: https://www.microsoft.com/sql-server/sql-server-downloads
2. Click Download under the edition you want: Evaluation, Developer or Express.
3. The downloaded file is called SQL2025-SSEI-Eval.exe, or Dev / Expr depending on the edition — around 4.2 MB.
4. Run that launcher and choose between three options:

5. Choose Download Media, select the ISO format and a destination folder.
6. Once the download finishes, mount the ISO on the target server and run setup.exe.

Step-by-step installation with the wizard

Step 1 — SQL Server Installation Center

When you launch setup.exe, the SQL Server Installation Center appears. In the left-hand pane:

• Planning: checks the prerequisites with the System Configuration Checker.
• Installation: launches the various installation scenarios.

Click Installation → New SQL Server stand-alone installation or add features to an existing installation.

Step 2 — Product key

Tip: you can install in Evaluation mode, for 180 days, and convert to a licensed edition later with the product key, without reinstalling.

Click Next.

Step 3 — Licence terms

Read and accept the Microsoft licence terms. Tick I accept the license terms and Privacy Statement.

This page also links to the Microsoft privacy statement. In a corporate environment, check that it complies with your GDPR policy.

Click Next.

Step 4 — Microsoft Update

This lets setup download the latest cumulative updates and apply them during installation. In production it is good practice, so that the server starts up already current.

Click Next.

Step 5 — Install rules

Setup automatically checks the installation rules:

• the .NET Framework is present;
• no restart is pending;
• registry access;
• the Windows firewall — a warning if port 1433 is not open.

If everything is green (✅ Passed), click Next. On a ⚠️ Warning about the firewall, you can configure the rules after installation.

Step 6 — Feature selection

This is one of the most important pages. Here is what each component does.

Instance features

Shared features

Installation directories

• Instance root directory: D:\Program Files\Microsoft SQL Server\ — avoid C:\.
• Shared feature directory: for the components shared between instances.

Good practice: never leave the SQL Server binaries on the system drive C:\. Use a dedicated volume.

Click Next.

Step 7 — Instance configuration

• Instance ID: the internal identifier used for the directories and registry keys.
• Instance root directory: confirm the path set in the previous step.

When should you use a named instance? When you have to host several SQL Server instances on the same server — a production instance plus a pre-production one, for instance. Each named instance has its own services, its own memory and its own ports.

Note: SQL Server Browser has to be running for clients to discover named instances.

Click Next.

Step 8 — Server configuration

This page has two important tabs.

The “Service Accounts” tab

Every SQL Server service runs under a Windows account. These are the configurable services:

gMSA (Group Managed Service Accounts) is the best practice in an Active Directory environment. Active Directory manages the password automatically, with no human intervention.

Startup options:

Set the Database Engine and the Agent to Automatic. Set the Browser to Automatic only if you have named instances.

Tick Grant Perform Volume Maintenance Task privilege to SQL Server Database Engine Service. This enables Instant File Initialization (IFI), which considerably speeds up the creation and growth of data files by skipping the zeroing of the disk blocks.

The “Collation” tab

The collation determines the sorting and comparison rules for character strings across the whole instance.

Why this is critical: the server collation applies to the system databases (master, model, msdb, tempdb) and becomes the default collation of every new database. It cannot be changed after installation without rebuilding master. Take the time to get it right.

Careful: if you have to work with existing databases, align the collation to avoid Cannot resolve the collation conflict errors.

Click Next.

Step 9 — Database Engine configuration

This is the richest page of the wizard. It has four tabs.

The “Server Configuration” tab

Authentication mode:

If you choose Mixed Mode:

• set a strong password for the sa account: 12 characters or more, upper and lower case, digits, special characters;
• the sa account is the number one target of attacks. In production, disable it after installation and use named accounts.

Specify SQL Server administrators:

Click Add Current User to add your Windows account as an administrator of the instance. Also add a DBA AD group, for instance DOMAIN\GRP-SQLAdmins.

Never leave this list empty. You would risk losing administrative access to the instance.

The “Data Directories” tab

This is where you set the default paths for the files:

The golden rule: always separate data files and transaction logs onto distinct volumes. Transaction logs use sequential writes and should not share a volume with the random I/O of the data files.

The “TempDB” tab

SQL Server 2025 offers an optimized automatic TempDB configuration from installation:

Why 8 files? TempDB is a contention hot spot. Multiplying the data files spreads the allocation requests across several files, which removes the latch waits on the system pages. Beyond 8, the marginal gain is negligible except on very specific workloads.

Every TempDB file must be the same size. SQL Server uses a proportional fill algorithm that distributes writes according to file size. Files of different sizes create an imbalance.

The “MaxDOP” tab

Since SQL Server 2019, the wizard proposes a recommended MAXDOP value based on the CPU topology it detects.

MAXDOP = 0 is discouraged. It means SQL Server uses every CPU for a single parallel query, which can saturate the server and block the other concurrent queries.

Accept the proposed value or adjust it. You can change it later.

The “Memory” tab

Since SQL Server 2022 the wizard also proposes the memory configuration:

The formula:

Max Server Memory = total_RAM - 4096 MB (OS) - RAM_for_other_services

Examples:

Why cap the memory? By default SQL Server consumes all the available RAM and does not give it back. Without a cap the operating system can run short of memory, causing slowdowns or crashes. max server memory is the first setting to configure on any production instance.

Click Next.

Step 10 — Ready to install

The summary page shows everything you selected:

• edition and product key;
• selected features;
• directory paths;
• service accounts;
• authentication mode;
• TempDB, MAXDOP and memory configuration.

Read this page carefully. It is your last chance to correct a mistake before the installation.

Tip: the path to the configuration file (ConfigurationFile.ini) is shown at the bottom of the page. Copy that file and keep it. You can reuse it for identical unattended installations on other servers:

setup.exe /ConfigurationFile="C:\SQLConfig\ConfigurationFile.ini" /IAcceptSQLServerLicenseTerms

Click Install.

Step 11 — Installation progress and completion

The installation generally takes between 10 and 30 minutes, depending on the hardware and the features selected. A progress bar shows where each component stands.

At the end, the Complete page shows the status of each feature:

• ✅ Succeeded: installed correctly.
• ❌ Failed: check the error log in C:\Program Files\Microsoft SQL Server\170\Setup Bootstrap\Log\.

If the installation fails, Summary.txt and the associated log folder hold the details of the error.

Click Close.

Installing SSMS (SQL Server Management Studio)

SQL Server 2025 works with SSMS 21 and SSMS 22. The tool is no longer included in the installation media.

1. Download SSMS from https://aka.ms/ssms/22/release/vs_SSMS.exe
2. Run the installer and follow the instructions.
3. Restart if prompted.

Post-installation configuration in SSMS

Connecting to the instance

1. Launch SSMS.
2. In the Connect to Server window:
   • Server type: Database Engine
   • Server name: SERVERNAME for a default instance, or SERVERNAME\INSTANCE
   • Authentication: Windows Authentication
3. Click Connect.

Server properties

Right-click the server in Object Explorer → Properties. Here is what each page holds.

The “General” page

Read-only information: server name, version, edition, OS, collation, memory, number of processors, root directory. Useful for a quick check of the configuration.

The “Memory” page

The T-SQL equivalent:

EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;

EXEC sp_configure 'max server memory (MB)', 28672;  -- 28 GB
RECONFIGURE;

EXEC sp_configure 'min server memory (MB)', 0;
RECONFIGURE;

The “Processors” page

The T-SQL equivalent:

EXEC sp_configure 'max degree of parallelism', 8;
RECONFIGURE;

EXEC sp_configure 'cost threshold for parallelism', 50;
RECONFIGURE;

Cost threshold for parallelism: the default of 5 is far too low for most production workloads. A value between 25 and 50 is a good starting point. It stops small queries from needlessly triggering a parallel plan, which consumes resources and threads.

The “Security” page

Recommendation: enable auditing of failed logins at the very least. It lets you detect intrusion attempts.

The “Database Settings” page

The T-SQL equivalent for backup compression:

EXEC sp_configure 'backup compression default', 1;
RECONFIGURE;

The “Advanced” page

The settings that matter:

The T-SQL equivalent:

EXEC sp_configure 'optimize for ad hoc workloads', 1;
RECONFIGURE;

EXEC sp_configure 'blocked process threshold (s)', 5;
RECONFIGURE;

Configuring the model database

The model database is the template for every new database. Configure it properly:

-- Reasonable initial size and growth
ALTER DATABASE model MODIFY FILE
(NAME = modeldev, SIZE = 256MB, FILEGROWTH = 64MB);

ALTER DATABASE model MODIFY FILE
(NAME = modellog, SIZE = 128MB, FILEGROWTH = 64MB);

Why? By default the initial size is 8 MB with percentage-based growth. That produces frequent auto-growth events and a proliferation of VLFs (Virtual Log Files), which degrades recovery performance.

SQL Server Configuration Manager

The SQL Server Configuration Manager (SQLServerManager17.msc for SQL Server 2025) is the system tool for managing the services, the network protocols and the client aliases.

Access: search for “SQL Server Configuration Manager” in the Start menu, or open compmgmt.msc (Computer Management), where it appears as a snap-in.

The Configuration Manager tree

SQL Server Configuration Manager
├── SQL Server Services
│   ├── SQL Server (MSSQLSERVER)          -- Database engine
│   ├── SQL Server Agent (MSSQLSERVER)    -- Job scheduler
│   ├── SQL Server Browser                -- Instance discovery
│   ├── SQL Full-text Filter Daemon       -- Full-text search
│   └── SQL Server Integration Services   -- SSIS, if installed
├── SQL Server Network Configuration
│   └── Protocols for MSSQLSERVER
│       ├── Shared Memory
│       ├── Named Pipes
│       └── TCP/IP
└── SQL Native Client Configuration
    ├── Client Protocols
    └── Aliases

SQL Server Services

Right-click a service → Properties.

The “Log On” tab

In production, always use a dedicated domain account or a gMSA. Never use Local System: it has excessive rights on the machine.

The “Service” tab

The “Startup Parameters” tab

The engine startup parameters:

You can add further parameters:

SQL Server Network Configuration — protocols

Shared Memory

• Use: local connections only, client and server on the same machine.
• Configuration: no options. Enabled by default.
• Production: leave it enabled, for local SSMS connections and maintenance scripts.

Named Pipes

• Use: LAN connections, mostly in legacy environments.
• Configuration: the pipe name, \\.\pipe\sql\query by default.
• Production: disable it unless you have a specific need. TCP/IP is preferable.

TCP/IP

This is the main protocol for network connections. Right-click → Properties.

The “Protocol” tab:

The “IP Addresses” tab:

Every network interface is listed — IP1, IP2 and so on — plus an IPAll section:

Production good practice:

• default instance: port 1433, fixed;
• named instance: assign a custom static port, 14330 for instance, rather than leaving a dynamic port;
• create a Windows firewall rule allowing the chosen port.

Configuring the firewall with PowerShell:

New-NetFirewallRule -DisplayName "SQL Server 2025" `
  -Direction Inbound -Protocol TCP -LocalPort 1433 `
  -Action Allow -Profile Domain

# For SQL Server Browser (UDP 1434) — named instances only
New-NetFirewallRule -DisplayName "SQL Server Browser" `
  -Direction Inbound -Protocol UDP -LocalPort 1434 `
  -Action Allow -Profile Domain

Important: after any change to the network protocols, you have to restart the SQL Server service for it to take effect.

SQL Native Client Configuration

Client Protocols

The order in which the client tries the protocols:

1. Shared Memory, for a local connection
2. TCP/IP
3. Named Pipes

You can change the order or disable a protocol by right-clicking → Properties under Client Protocols.

Aliases

Aliases create alternative connection names pointing at a specific server and port. Useful for:

• changing server without touching the connection strings of your applications;
• using a logical name (SQL-PROD) instead of a technical one (SRV-SQL-PRD-01\INST01,14330).

Post-installation checks

Run these T-SQL queries to validate the configuration:

-- 1. Version and edition
SELECT @@VERSION;
SELECT SERVERPROPERTY('ProductVersion')   AS Version,
       SERVERPROPERTY('Edition')          AS Edition,
       SERVERPROPERTY('ProductLevel')     AS ServicePack,
       SERVERPROPERTY('Collation')        AS Collation;

-- 2. Memory configuration
SELECT name, value_in_use
FROM sys.configurations
WHERE name IN ('max server memory (MB)', 'min server memory (MB)');

-- 3. MAXDOP and cost threshold
SELECT name, value_in_use
FROM sys.configurations
WHERE name IN ('max degree of parallelism', 'cost threshold for parallelism');

-- 4. Optimize for ad hoc workloads
SELECT name, value_in_use
FROM sys.configurations
WHERE name = 'optimize for ad hoc workloads';

-- 5. TempDB: number of files and sizes
SELECT name, physical_name, size * 8 / 1024 AS [Size_MB],
       growth * 8 / 1024 AS [Growth_MB]
FROM sys.master_files
WHERE database_id = DB_ID('tempdb');

-- 6. Backup compression
SELECT name, value_in_use
FROM sys.configurations
WHERE name = 'backup compression default';

The post-installation architecture

graph LR
    subgraph "Windows Server"
        OS["OS + 4 GB RAM reserved"]
        FW["Windows firewall<br/>TCP port 1433"]
    end
    subgraph "SQL Server 2025"
        ENG["Database Engine<br/>(sqlservr.exe)"]
        AGT["SQL Server Agent<br/>(sqlagent.exe)"]
        BRW["SQL Server Browser<br/>(sqlbrowser.exe)"]
    end
    subgraph "Storage"
        D["D:\ Binaries"]
        E["E:\ Data (.mdf/.ndf)"]
        F["F:\ Logs (.ldf)"]
        G["G:\ TempDB"]
        H["H:\ Backups (.bak)"]
    end
    subgraph "Protocols"
        SM["Shared Memory"]
        TCP["TCP/IP :1433"]
        NP["Named Pipes"]
    end

    ENG --> D
    ENG --> E
    ENG --> F
    ENG --> G
    ENG --> H
    ENG --> SM
    ENG --> TCP
    ENG --> NP
    TCP --> FW
    AGT --> ENG
    BRW --> |UDP 1434| FW

Production configuration checklist

graph TD
    A[Installation finished] --> B{Max Server Memory set?}
    B -->|No| B1[Set it now]
    B -->|Yes| C{MAXDOP set?}
    C -->|No| C1[Set it according to NUMA]
    C -->|Yes| D{Cost threshold ≥ 25?}
    D -->|No| D1[Raise it to 25-50]
    D -->|Yes| E{TempDB: 4-8 files?}
    E -->|No| E1[Add files]
    E -->|Yes| F{Instant File Initialization on?}
    F -->|No| F1[Enable it through gpedit.msc]
    F -->|Yes| G{Backups configured?}
    G -->|No| G1[Set up a maintenance plan]
    G -->|Yes| H[✅ Ready for production]

The essential sp_configure commands

-- Enable the advanced options
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;

-- Memory
EXEC sp_configure 'max server memory (MB)', 28672;
RECONFIGURE;

-- Parallelism
EXEC sp_configure 'max degree of parallelism', 8;
RECONFIGURE;

EXEC sp_configure 'cost threshold for parallelism', 50;
RECONFIGURE;

-- Plan cache optimization
EXEC sp_configure 'optimize for ad hoc workloads', 1;
RECONFIGURE;

-- Backup compression
EXEC sp_configure 'backup compression default', 1;
RECONFIGURE;

-- Blocked process threshold, for monitoring
EXEC sp_configure 'blocked process threshold (s)', 5;
RECONFIGURE;

-- Final check
SELECT name, value_in_use
FROM sys.configurations
WHERE name IN (
    'max server memory (MB)',
    'min server memory (MB)',
    'max degree of parallelism',
    'cost threshold for parallelism',
    'optimize for ad hoc workloads',
    'backup compression default',
    'blocked process threshold (s)'
)
ORDER BY name;

Further reading

• Microsoft documentation — installing SQL Server 2025
• Hardware and software requirements
• What is new in SQL Server 2025
• SQL Server Configuration Manager
• Server configuration options (sp_configure)