Shop Talk: 2020-03-29

The Recording

The Panelists

  • Kevin Feasel
  • Mala Mahadevan
  • Mike Chrestensen

Notes: Questions and Topics

Deleting Backup Files

@rajeshparuchuri asks, “How do you delete old backup files? Or what is your preferred way of deleting old backup files?”

We had some discussions about different methods for deleting, but there are several key methods:

  • Use xp_cmdshell to delete the files. This wasn’t available to Rajesh, so we had to move on.
  • Write a PowerShell script to delete the files and call that script in the backup job. Essentially, know where the backups are stored and write a one-liner to get child items (with a .trn or .bak extension), filter to get just those older than your retention period, and delete the objects.
  • Use a maintenance plan. I include this in the list for the sake of completeness, not because it’s a great idea.
  • If you’re writing backups to a cloud store like AWS S3 or Azure Blob Storage, you can set a retention plan on the bucket/container and automatically delete files older than a certain age.
  • Similarly, many newer SANs offer the ability to set a retention policy on a share.

The Downside of Storing VARBINARY in a Table

@rednelo7625 asked: “I have a question about storing Word docs in a document DB as VARBINARY(MAX). I’m limiting my users to an upload size of 3MB. I’m storing them this way so that I can encrypt them and back them up. Do you see any problem with this practice?”

The short answer is yes, there are some risks with this. The biggest problem is that if the database becomes really popular, it can bloat up quickly and make activities like database backups, CHECKDB runs, etc. run a lot slower. And with blob data like this, there’s not much we can do about it—especially something like DOCX files which are already zipped (spoiler: .docx is basically a zipped series of XML files), so you don’t get any real compression benefits from using COMPRESS().

As for the reasoning, it’s to encrypt and back up files. My response was to recommend checking into FileTable functionality that was introduced in SQL Server 2012. FileTable gives you a nice compromise between a desire to keep file metadata in SQL Server while keeping the binary data out. If you take a full backup of your database, it does back up the FileTable data (unless you choose to exclude it), so you do get backup protection that way without needing to store the files directly in the database.

As far as encryption goes, I’d recommend enabling disk-based encryption on the storage where those files are (assuming you use FileTable). I made the guess that rednelo was using Transparent Data Encryption for this, and encrypting the disks provides a similar level of protection—it protects data at rest. For further protection, it would be possible to write an app which accepts those Word documents and saves them in a password-protected archive, or encrypts the binary data and saves it as an encrypted file, decrypting it later for access.

IoT Everywhere

Eventually, we got pulled off onto a sidetrack around IoT, especially in agriculture. This is an area of interest to me because the average person has no clue just how sophisticated modern agriculture is. Anders and @ENHANCE_QC have some knowledge in the area (family members in farming) and added some nice context too.

We covered one of the key problems with IoT: you may own the hardware, but if it has to talk to a remote server to survive, your expensive product can quickly become a brick. This also ties to right-to-repair laws, which I fully support. My philosophy on this is that if I bought the product, I should be able to alter the product, including repairs and modifications.

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