08Nov, 2021
Your Sitecore Managed Cloud Disaster Recovery Backups Will Fail When Enabled, but That's Ok, Backup Filters Are a Thing
Part of managing your hosted Sitecore instance is going to be configuring Disaster Recovery. When provisioned, the out-of-the-box filters provided by Sitecore will likely not be enough to avoid errors, so it should be updated to exclude some big areas.
Looking at the directory of your Sitecore instance, be it Content Management or Content Delivery, you'll find this newly created file, called _backup.filter:
The purpose of this file is to define exclusions from your Azure backups. Sitecore helps with adding the following locations, but it's not going to be enough:
\site\wwwroot\App_Data\debug \site\wwwroot\App_Data\viewstate \site\wwwroot\temp \site\wwwroot\bin\Sitecore.ContentIndexing.WebApi.dll \site\wwwroot\sitecore modules\Web\ExperienceExplorer\Assets\vendors\jquery-ui\images
When the first backup ran I received emails with the following error in it:
The website + database size exceeds the 10 GB limit for backups. Your content size is 10.4 GB. Try using a backup.filer file to exclude some files from the backup as described here https://aka.ms/partial-backup, or try removing the database portion of the backup and use externally offered database backups instead.
So it's pretty straightforward, and you could increase the size limit, but the trick to getting it working without that is to root around your root and find more disposable items to exclude. In my case I found the following areas that could be added:
\site\wwwroot\App_Data\DeviceDetection \site\wwwroot\App_Data\logs \site\wwwroot\App_Data\diagnostics \site\wwwroot\App_Data\MediaCache \site\wwwroot\App_Data\packages \site\wwwroot\App_Data\mediaIndexing \site\wwwroot\App_Data\serialization
Once these were added, I updated our repo and deployed the file, went to my Sitecore instance in Azure -> Backups -> manually triggered a backup. Here you can see it was a success, and the regular intervals also completed with no issue.
One Mote Thing
One more thing to note, is the _backup.filter file will not be created in any deployment slots you've already created, so if you swap them your errors will come back. I've added the filter file to our regular deployments so we also have some version control over it, on top of ensuring it's always installed
