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Category: Corruption

An Outage from Corruption

Published 2026-09-09 by Kevin Feasel

Rob Farley tells a story:

Naturally when there’s a failure, there are questions about High Availability solutions. If the customer has an Availability Group, maybe they’ve avoided an outage completely – the primary fails over to the secondary, and the race starts to get the original machine back in case another failure (on the new primary) happens. Those situations aren’t the ones that keep coming back to mind, but are still stressful for the temporary loss of the safety net.

The bigger issues are when there is no quick failover available. About thirty years ago, I was dealing with a SQL Server 6.0 environment, where the customer’s DBA was cycling tapes (yes, tapes) for differential backups, except that he’d reused the tape that the full backup was on. When that system went down, I had a quick and harsh introduction to salvaging files off the disks from a failed computer. Fun times.

Also, it sounds like Rob’s surgery from last month has gone well, so hopefully he remains on the road to recovery.

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Data Corruption in PostgreSQL

Published 2026-01-06 by Kevin Feasel

Josef Machytka explains a new (for PostgreSQL) solution to an old problem:

PostgreSQL 18 made one very important change – data block checksums are now enabled by default for new clusters at cluster initialization time. I already wrote about it in my previous article. I also mentioned that there are still many existing PostgreSQL installations without data checksums enabled, because this was the default in previous versions. In those installations, data corruption can sometimes cause mysterious errors and prevent normal operational functioning. In this post, I want to dissect common PostgreSQL data corruption modes, to show how to diagnose them, and sketch how to recover from them.

Read on to learn more, as well as what this new change means.

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Postgres Index Corruption after an OS Upgrade

Published 2025-12-16 by Kevin Feasel

Laurenz Albe has me concerned:

Most major Linux distributions have upgraded to the GNU C library version 2.28 or later. Therefore, there is a growing awareness that an operating system upgrade can lead to index corruption. However, rebuilding all your indexes can slow down the upgrade process considerably. In this article, I want to discuss how you can avoid rebuilding more indexes than necessary.

Read the whole thing if you are a Postgres DBA.

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Restoring a Single Data Page in SQL Server

Published 2025-04-23 by Kevin Feasel

Stephen Planck turns the page:

Most of the time, corruption in SQL Server is either nonexistent or so widespread that you have no choice but to perform a file or full‑database restore. Yet an awkward middle ground exists: a handful of pages—perhaps only one—become unreadable while the rest of the database remains perfectly healthy. A full restore would repair the damage, but at the cost of rolling back hours of work and locking users out of an otherwise functional system.

That is precisely why Microsoft built RESTORE … PAGE. When you meet a short list of prerequisites (FULL or BULK_LOGGED recovery model, an unbroken backup chain, and a page that is not allocation metadata), you can surgically overwrite just the bad 8‑KB chunks, roll them forward with transaction‑log backups, and return the database to service in minutes rather than hours.

Read on to see how it all works, as well as situations in which this isn’t the right answer.

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Automating DBCC CHECKDB on Full Backups

Published 2025-01-15 by Kevin Feasel

Shane O’Neill riffs off of a script:

Like many shops out there, we can’t run corruption checking on our main production database instance. So, then, what do we do? We take the backups and restore them to a test instances, and then run corruption checking on those restored databases.

At least this way we can test the backups we take can be restored, as well.

But, I don’t want to spend every day manually restoring and corruption checking these databases, so let’s automate this bit…

Click through for a script that Shane built off of a Madeira Data Solutions script that Eitan Blumin put together.

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Dealing with Corruption around In-Memory OLTP

Published 2021-08-25 by Kevin Feasel

Chris Taylor has a tale of woe:

Late last week (20th) we had an emergency call from a company that had a production database go into Suspect mode and needed help. Now this isn’t a great situation to be in so when they then go on to tell us that the last valid backup they had was from the 12th and the backup job had been failing since then – even less of a great situation to be in

Read the whole thing.

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Fun with Database Corruption

Published 2021-06-23 by Kevin Feasel

Chad Callihan isn’t in production:

When you’re not expecting it, database corruption is bad for your database server (and probably your own personal health). Database corruption can be fun though when you’re the one doing the corrupting. Let’s take a look at corrupting a database and see what we can learn.

Click through to see what kind of madness you can pull off and how to fix it. And if you get really excited about database corruption, check out Steve Stedman’s Database Corruption Challenge.

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Stellar Repair: A Review

Published 2020-09-25 by Kevin Feasel

Grant Fritchey reviews a product which attempts to repair corrupted SQL Server databases:

Let’s start with the most important piece of information you need: it works.

The software itself is really simple to use and just does what you need, repairs your corrupted SQL Server instance. On that alone, I can recommend the tool.

However, there are a few gotchas I ran into along the way. Mostly, little stuff. It’s things a little polish in the UI and some clean up around language could help out. Don’t get me wrong, I’m happy with this software. It worked. It’s just how it works that we should talk about.

Click through for Grant’s full review.

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