Can you estimate how much data a 1TB external hardrive would be able to store? Like 8hr school day, so 1 years worth? Cause if I were a teacher, then I would spend my own $ on a 1TB hardrive to protect myself. I mean they already spend their own money to decorate classes.
The short answer to the question is "Yes, the storage needs can be calculated." But, that is only the beginning of determining what you can and should include as a solution for storing video and audio of teachers.
It's not feasible to expect any system to let you donate a 1TB disk for a pooled A/V recording store. The disks need to be spec'ed to work together, provide the performance and capacity necessary to manage the files, and work with the hardware in place. USB is usually not fast enough to record multiple A/V streams at once. On top of the performance factor is the reliability factor. My experience has been that too many external USB drives fail in a very short time. Maybe it's the design, people taking them from place to place, or whatever else, but I don't trust any of them -- even if they are just sitting plugged into a PC all the time. I use these for short term storage, like moving files from one machine to another. But the storage is temporary on the USB externals. I've had to return almost every Seagate 3.5" external disk from COSTCO I've purchased. Some died within a year or less. Luckily, Costco's return policy let me get a full refund on drives that were way outside the warranty period.
I'm talking years later! The Seagate 2.5" externals seem to last pretty well -- no problems with any of them.
The calculations depend on a variety of variables. Here are a few:
- the compression format being used to record and store the video and audio
- the resolution, frames per second and quality of the video and audio
- the number of cameras per capture device (size and resolution is often limited as the number of cameras/mics per capture device increases)
- whether the stream is compressed by the CPU or the capture device. CPU compression may not keep up with a dozen or more cameras
Sometimes you can capture the stream in high quality audio and video without compression to reduce load on the recording machine (requires much more storage), then use an archiving process to take that video, compress it as far as possible, and write it to a RAID for long-term storage.
It's not feasible for any system of this size to use a 1TB drive, especially external drives that tend to not last long, and with limited speeds over USB compared to SATA and NVMe throughput. We'd be talking about arrays of 10TB, 12TB or 18TB or more per disk, all contained in arrays to provide redundancy for hardware and software failures.
I have 4 cameras on an older capture card that records 24/7/365, and it "wraps around" to overwrite the oldest video when full. Each disk is 1TB, and I have 2 disks. Full quality for that card is 60fps at 720 lines per inch of resolution. No audio gets recorded. The disks can record without overwriting for about a month.
As with each A/V DVR recording system, there is overhead involved with the storage devices as well. Disks have to be prepared to work with a given DVR software program. The recordings are stored as smaller segments to facilitate searching and copying. Massive video files are a b*tch to copy and edit for runtime. Watermarks also take up space, a necessity if the video is ever authenticated for use in a court case or official complaint.
More and more, arrays are switching over to SSD storage. The speed and reduced infrastructure requirements make it great for these large scale applications, but the cost is still very high for the largest capacity SSDs.