SQL Server Administration on Rudi Bruchez

SQL Server Standard: understanding Basic Availability Groups (BAG)

Tue, 27 Jan 2026 00:00:00 +0000

TL;DR

Basic Availability Groups (BAG) give SQL Server Standard edition users high availability similar to the Always On AG of the Enterprise edition, but with significant limitations:

One group per instance.
One database per group.
No reads on the secondary replica.
No backups on the secondary.
Two nodes maximum, primary and secondary.

For a long time, using Always On Availability Groups required an Enterprise licence, leaving Standard edition users with Database Mirroring. Since SQL Server 2016, Microsoft has offered Basic Availability Groups (BAG) as the replacement for mirroring in the Standard edition.

Always On: mastering the timeouts

Tue, 27 Jan 2026 00:00:00 +0000

TL;DR

To avoid spurious failovers in an Always On environment, adjust these settings:

Lease Timeout: raise it if your server goes through CPU load spikes.
HealthCheck Timeout: raise it if your server is slow to answer diagnostic requests.

When you run AlwaysOn Availability Groups, it is not unusual to get spurious failovers while your system is working perfectly well.

It tends to happen at night, and more rarely during the day. The most common cause is a temporary unavailability of the system, which makes the cluster health checks time out. A typical example is a VM freeze while backup software takes a snapshot.

Basic counters

Mon, 01 Jan 0001 00:00:00 +0000

Here is a list of the Windows and SQL Server performance counters to watch, to make sure SQL Server is running properly.

Processor / % Processor Time

Total processor time as a percentage, and per core where useful, to watch how the threads are distributed.

Physical Disk / Avg. Disk sec/Read

Watch this on the disks holding the SQL Server data files.

It is the average time in seconds of a data read from disk — a latency measurement. Depending on the type of disk, local or remote, the value should ideally stay below .025, that is 25 milliseconds of latency.

Monitoring with PRTG

Mon, 01 Jan 0001 00:00:00 +0000

PRTG Network Monitor is a commercial monitoring product from Paessler. This guide explains how to configure it to monitor SQL Server.

There does not appear to be a package or counter group tailored to SQL Server natively in PRTG. You have to add them by hand.

To do that, add a “Windows PerfCounter Custom” sensor, and register the Windows performance counters related to SQL Server.

The simplest approach is to look the counters up directly on the SQL Server machine to identify the ones you care about, then enter them by hand in PRTG.

SQL Server transaction log backups: why and how

Mon, 02 Mar 2026 00:00:00 +0000

TL;DR

A SQL Server transaction log growing out of control, because the database recovery model is FULL, is one of the most common problems you will meet with SQL Server.

Administrators often switch to the SIMPLE recovery model to avoid it, wary of managing a transaction log backup strategy — when that strategy is very nearly mandatory in production.