The retention time of an SD card is defined as the number of days that the card has stored data before it starts to erase and rewrite data. Some regions require data used for evidence to be stored for between 30 and 180 days, so maximum retention time is an important factor to consider in a recording solution.
Axis surveillance cards offer long maximum retention times even at high frame rates and resolutions, with no compromise on recording quality. The maximum retention time depends on how the camera is configured to record at different frame rates and resolutions, depending on motion detection, alarm events and hours of the day.
For example, the maximum retention time of an Axis surveillance card with 128 GB storage could typically vary from 20 to 215+ days, depending on the camera configurations and resolution required. Even smaller 64 GB cards’ maximum retention times can range from 10 to more than 100 days. For larger cards, such as 256 GB and up, maximum retention times will, of course, be much longer.
You can configure the retention time you need in the camera’s web interface. If you select, for instance, a retention time of one week, a clean-up operation will remove all recordings older than 7 days. This operation runs once every 60 minutes. There is also an automatic clean-up operation that runs continuously to check that the card has enough space for recording.