How many days should camera footage be kept? How to calculate disk capacity

How many days of footage is enough?

The right period depends on how long after a problem is noticed. In a grocery store, a cash register discrepancy often shows up at the end of the day or at the weekend count. In a warehouse, missing goods may be understood at the month-end count. In an apartment building, the owner sees the next morning that their car was hit and the driver fled. The footage should be kept longer than that noticing time.

Extending the retention period is not always good. Video recordings are personal data under Law No. 6698 on the Protection of Personal Data (the Turkish Personal Data Protection Law), and the law requires that data not be kept longer than the time necessary for the purpose it is processed for. There may also be separately set periods in some sectors. When determining the right period for your business, we recommend consulting a legal expert.

In practice, most businesses set a period by adding a few days of margin to the time it takes to notice an incident, and set the recorder to fill that period. When the period is full, the device overwrites the oldest footage.

What determines the disk need?

The space a camera takes on the disk depends on the amount of data it produces per second, that is, the bit rate. The bit rate is in turn determined by several settings together:

• Resolution: a 4 MP camera produces more data than a 2 MP camera at the same settings.
• Frames per second: security recording often does not need full smoothness.
• Compression type: H.265 stores the same image with less data than H.264.
• Motion in the scene: a crowded store produces more data than an empty corridor.
• Recording mode: continuous recording, or recording only when there is motion?
• Night image: the noise that appears in the dark can raise the bit rate.

Disk calculation step by step

The calculation is a simple multiplication. You multiply the camera's bit rate (megabits/second) by the number of seconds in a day, that is, 86,400. You convert the resulting megabit value to megabytes by dividing by 8. When you multiply this by the number of cameras and the number of days to keep, the total need comes out.

As an example, let us consider a camera recording continuously at 4 Mbps. 4 x 86,400 = 345,600 megabits, which divided by 8 comes to about 43 GB per day. Thirty days of this camera's footage takes up about 1.3 TB. For 8 cameras at the same setting, 30 days requires about 10 TB of disk. The 4 Mbps here is only an example; you can see your own camera's bit rate in the recorder's channel settings.

You can do this calculation quickly by entering the number of cameras, the resolution and the number of days you want into the disk calculator on our site.

Expert note: Do not choose the disk right at the limit. There is a difference between the capacity the manufacturer states for the disk and the usable space the device sees, and the need grows as cameras are added. Leave a margin on top of the calculation.

Does motion recording save space?

Recording only when there is motion makes the disk last much longer in a warehouse or office that stays empty all night. This has a cost: if detection is not set correctly, the first seconds of an incident may be missed, or unnecessary footage may pile up because of leaves, shadows and insects.

Cameras that can tell people and vehicles apart reduce this problem considerably. Another method is mixed recording: the camera records continuously at a low bit rate and switches to high quality when there is motion. This way you get both continuous recording and detailed footage at the moment of an incident.

At critical points such as the cash register, the entrance door and the parking lot, continuous recording is preferred. In the back warehouse, on the roof or in corridors not used at night, motion recording may be enough. Deciding separately for each camera uses the disk budget more efficiently.

Choosing the disk and the recorder

The capacity you calculated has to fit into the recorder's disk bays. A small device with one bay cannot take more than the largest disk it supports. If a long retention time or many cameras are needed, a device with two or more disk bays is chosen.

For recording, security disks designed for continuous writing are used. Desktop computer disks are not made for writing all day, so they can wear out faster. Checking the disk's health from the recorder's menu now and then lets you notice a failure before footage is lost.

When an incident happens, export the relevant footage right away and keep it in a separate place. When the period runs out, the recorder overwrites that footage, and it may not be possible to get to the footage weeks after the incident.

Who should access the footage, and how?

As much as the retention period, who can access the stored footage matters too. On the recorder, only one or two people should know the admin password, and other staff should be given live viewing permission only. If the permission to rewind and export footage is kept limited, it becomes harder for a recording to be copied or deleted without permission.

When footage is exported because of an incident, it is a good habit to note in a simple notebook or file who did it, on what date and for what purpose. If the footage is going to be given to an official authority, this note also helps show that the footage was not altered.

Putting up a notice sign at the entrance of areas with cameras is also one of the steps expected under KVKK. Get support from an expert for the content of the sign and the details of the disclosure obligation.

Factors that shorten disk life in Şanlıurfa

A recorder working in a cabinet with no ventilation in the summer heat runs its disk at a high temperature. Heat and frequent power fluctuations are among the main factors that shorten disk life. Placing the device in a cool, ventilated place and a UPS: connecting the recorder to it reduces disk failures and recording gaps.

Dust is another overlooked factor. When the recorder's fan and air vents clog with dust, the temperature inside the device rises. Cleaning the fans during maintenance is a simple but effective precaution.

During installation, Desa Bilişim sets the bit rate per camera, and a few days after installation it checks that the recording period you asked for is really being achieved.

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