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Category: HA / DR

Online DR from SQL Server 2022 and Azure SQL MI Now Available

Published 2024-10-10 by Kevin Feasel

Djordje Jeremic announces general availability of one of the key selling points from SQL Server 2022:

Today, we are announcing the general availability of the following two major capabilities of the Managed Instance link feature with SQL Server 2022:

  • Two-way failover between SQL Server 2022 and SQL Managed Instance through the link to unlock true disaster recovery (DR) with Azure
  • Creating a link from SQL Managed Instance to SQL Server 2022 to unlock off-PaaS data mobility for regulatory and dev/test scenarios 

Click through for more detail.

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pgBackRest and Standby Server Backups

Published 2024-09-23 by Kevin Feasel

Stefan Fercot does some explaining:

Recently, we’ve received many questions about how to take backups from a standby server using pgBackRest. In this post, I’d like to clarify one of the most frequently asked questions and address a common misconception for new users.

First of all, it’s important to understand that taking a backup exclusively from the standby server is not currently possible. When you trigger a backup from the standby, pgBackRest creates a standby backup that is identical to a backup performed on the primary. It does this by starting/stopping the backup on the primary, copying only files that are replicated from the standby, then copying the remaining few files from the primary.

Read on to learn more and to see an example of how this works.

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Resuming Data Movement for an Availability Group

Published 2024-08-21 by Kevin Feasel

Chad Callihan gets things moving after a few 1s without enough 0s clog up the pipe:

Keeping an Always On Availability Group healthy is crucial, and seeing a non-synchronizing database in an Always On High Availability Group can give you a sinking feeling (pardon the pun). Disregarding the reason for the syncing issue, there are a few ways to resume syncing and get your setup back in the green.

Let’s look at resuming using the SSMS GUI and running a SQL statement.

Read on for the process. I appreciate that Chad also includes the T-SQL operation to do this.

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SQL Server on Linux for Disaster Recovery

Published 2024-08-19 by Kevin Feasel

Mika Sutinen shares a use case:

SQL Server on Linux has been an option for quite a while already, but I have to admit that personally, I have previously not been a very excited about that idea. This is mostly due to some complexities and limitations of SQL Server on Linux. However, the recent CrowdStrike incident made it quite obvious, that there’s a great use case for it. And that use case is Disaster Recovery.

The idea of having some operating system variety makes sense, though read the whole thing, as some companies will use components that SQL Server doesn’t offer for Linux.

And if you want a deep dive into using SQL Server on Linux, I’ll do a bit of self-promotion and reference my video series on the topic.

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Building a SQL Server Failover Cluster in Google Cloud Platform

Published 2024-08-19 by Kevin Feasel

Dave Bermingham talks about availability:

Building a SQL Server Failover Cluster in Google Cloud Platform (GCP) is a powerful way to ensure your databases remain highly available, even in the face of unexpected failures. High Availability (HA) is crucial for any business-critical application. Downtime can mean lost revenue, decreased productivity, and even damage to your company’s reputation. However, creating HA clusters in the cloud, especially in GCP, presents unique challenges—most notably, the lack of shared storage, which has traditionally been a key component of SQL Server Failover Clustering.

Click through for an overview and a whitepaper on the topic.

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Failover Groups in Azure SQL Database

Published 2024-04-08 by Kevin Feasel

Josephine Bush sets up a failover group in Azure SQL Database:

In today’s fast-paced digital world, keeping your data safe and accessible is more important than ever. That’s where Azure SQL Database steps in, offering a suite of tools to ensure your information is always within reach. Among these tools, failover groups shine, ready to jump into action whenever there’s a hiccup. So, let’s explore how failover groups in Azure SQL Database work their magic, ensuring your data stays safe and sound despite unexpected challenges.

Read on for the step-by-step instructions.

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Forced Quorum Failures with WSFC

Published 2024-02-13 by Kevin Feasel

Eitan Blumin can’t reach quorum:

The incident started with a late-night phone call from one of our customers (it’s always a late-night phone call, isn’t it?).

They reported that during a DR exercise on their production environment (Chaos Engineering, anyone?) their entire cluster failed and they weren’t able to bring any of the replicas back online.

Click through for the full story, including what happened, why it happened, and what you can do to prevent similar problems in the future.

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SQL Server Failover Clusters in Linux

Published 2024-02-07 by Kevin Feasel

I phone it in:

In this video, we will talk about Failover Cluster Instances in SQL Server on Linux.

This video stays in the academic realm because I don’t have an enterprise version of Linux (either RHEL or SLES) and don’t have a SAN or NAS, so I couldn’t actually show any of it off. Still, somehow I turned the utter lack of demo into almost a 20-minute video.

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Backups Are for DR, Not HA

Published 2023-10-18 by Kevin Feasel

Kevin Hill gives us a poignant reminder:

Please continue doing your backups!

Backups are Disaster Recovery, yes…but not HA.

Some will argue with this (in the comments most likely), but I broadly define “High Availability” as a system that can recover in seconds or minutes at most. Sometimes that is automatic, sometimes manual.

I agree that backups are for DR, not HA. I’d consider log shipping an option for both HA and DR, albeit one that requires manual failover (or rigging up a script that performs the failover for you).

I disagree about replication as an HA solution. Yes, you do need to make sure that everything can replicate, but if your publisher goes down, the subscriber can continue and your data is still available for use. And if you’re a complete masochist, you can use merge replication to allow writes to continue while the publisher is down. Cleaning up after that is a mess, especially if you end up with a bunch of conflicts, but High Availability doesn’t mean Easy Mode.

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Hybrid Failover Rights from SQL Server 2022 to Azure SQL MI

Published 2023-10-11 by Kevin Feasel

Dani Ljepava explains a new benefit:

Hybrid failover rights is a new benefit that allows you to run a license-free Azure SQL Managed Instance when used as a passive DR replica for your SQL Server 2022 licensed under Software Assurance (SA), or using Pay-as-you-go billing option.

How the Hybrid Failover Rights benefit works

The new Hybrid failover rights licensing benefit is technology agnostic. You can use any technology, such is MI link as the most advanced replication technology using Always On, or perhaps LRS, ADF, transactional replication, backup and restore, or similar to setup replication between SQL Server and Managed Instance. As long as you are using Azure SQL Managed Instance only as a passive replica for your SQL Server 2022, you are eligible to apply the new licensing benefit.

Read on for more details on how you can activate this benefit.

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