Category: Backups

Ned Otter gives us some options for reducing the size of full backups:

SPARSE columns

IF a column contains mostly NULLs, then depending on the data type, you can achieve space savings by using the SPARSE property (documentation here). SPARSE columns can be used with filtered indexes to theoretically reduce storage space and increase query performance. But there are a boatload of gotchas, such as issues with query plan caching (filtered indexes), and the fact that if you use SPARSE columns, neither the table or indexes can have any form of compression (the documentation is clear about not supporting table compression, but does not mention index compression being an issue – but it is).

As the documentation clearly states, when converting a column from non-sparse to sparse, the following steps are taken:

1. Adds a new column to the table in the new storage size and format
2. For each row in the table, updates and copies the value stored in the old column to the new column
3. Removes the old column from the table schema
4. Rebuilds the table (if there is no clustered index) or rebuilds the clustered index to reclaim space used by the old column

For large tables with even a few columns that you wanted to convert to SPARSE, this process would take forever, because you must do this for each column you want to convert.

I don’t like sparse columns at all, but I do like the rest of Ned’s options.

Grant Fritchey digs into one of the more contentious areas of GDPR:

Nothing within Article 17 talks about backups, offsite storage, readable secondaries, log shipping, or any of that stuff. In fact, there’s nothing technical there at all. No help to tell you what to do about this question.

Now, each article has expansions that further detail the information within the article called recitals. In the case of the right to be forgotten, there are two, Recital 55 and Recital 66. Recital 55 has nothing for us, at all. Recital 66 does talk about the fact that, because we’re dealing in an online world, the best available technical means should be used to deal with the fact that a person’s data may be in more than one location and we’ll need to clean that up.

And that’s it.

In fact, you can search the GDPR and not find the word, backup.

Read on for Grant’s thoughts, including what he argues is a defensible position (though we won’t know for sure until the bureaucracy runs its course).

Kenneth Fisher makes a great point regarding backups:

I’ve said before that backups are at once one of the easiest things DBAs do, one of the most important, and one of the most complicated. Take a full backup, restore it. Pretty simple right? And yet it’s vital when accident or corruption require recovering data. And as simple as it can be on the surface, the more you dig, the more there is to know, and the more complicated it can become. Well, one of those complications is the backup of the backup files. I mean, assuming you are using native backups, that full backup is sitting on a drive somewhere, and hopefully, that drive gets backed up right?

Why? Well, for performance purposes you probably back up your databases locally. To a drive attached to the server. Now you may not, heck you could be backing up to Azure, but for the sake of this argument let’s say you are. Part of a careful disaster recovery plan is making sure you have access to those backups. I’ve heard stories of entire data centers going underwater (literally). You need to at least have a copy of your backups in a separate system, separate location from production.

The proliferation of S3/Blob Storage for “warm” backups and Glacier/Cool Blob Storage for “cold” backups has made it much cheaper to retain longer-term backups.