In the scenario that the surveillance video storage can only save data for one month, because the surveillance system usually stores the video in a cyclic overlay way, when the new video data is generated and exceeds the set storage period (here is 1 month), the earlier video data will be automatically overwritten to make room for new video. This means that the data on the physical storage medium (such as a hard disk) has been written to the new video content, and the old data has been logically or even physically erased.
In this case, if no form of backup of the original video data has been made, once it has been overwritten, the overwritten data cannot be read directly by conventional technical means alone. Because modern hard drives do not retain traces of the original data when overwriting data, except in very special circumstances, such as some data is not completely overwritten and there may be a very small probability of retrieving some information through professional data recovery tools and methods, this is not the norm of reliability.
Therefore, for a surveillance video system that can only be stored for one month, without an additional backup strategy, users really cannot access the video data before this time period.
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