How many days can surveillance footage be stored? The 2TB hard drive was supposed to be stored for three months, but I ran it for a week with continuous recording

Last month, my colleague Lao Zhou's house wanted to install surveillance cameras and asked me what size hard drive I should buy. I blurted out: "2TB, I guess. I can save for two or three months." I heard this two years ago when I was installing surveillance cameras myself, and I've always told people this. That night, when I got home, I casually flipped through the earliest video on my drive, and when I saw the date, I was stunned—only nine days ago was left. For a 2TB drive, just over seven days old, I started erasing the oldest footage and cycling to write a new one. The advice I give others is more than four times worse than my own family's actual situation. This article will recalculate the entire account from the beginning. After reading, you will know how big a tray and video to buy for your home and why the video "disappeared on its own."

first calculate the numbers: how much to record in a day, and do it yourself in five minutes

how much video space it occupies, it follows just one count: video stream. The 4Mbps and 2Mbps settings in the camera settings are these, meaning how many megabytes of data are written to the hard drive per second. Converted to a daily amount, it's just one step: bitrate divided by 8 gives MB written per second, then multiplied by 86,400 seconds per day.

use my home as an example. All six connectors have 4MP pixels, encoded H.265, and the main stream is set to 4Mbps. Dividing by 8 means writing 0.5MB per second, which means about 43GB per day. Writing six heads at once costs about 260GB per day. After formatting this 2TB drive, you can use 1.8TB, 1800 divided by 260, seven days. This is what is happening at home. Numbers don't lie; what lies is my assumption of "three months."

this table applies to both NVR recorders and NAS, and the logic for recording to the disk is the same. Some may ask: Is the seller's claim of "2TB deposit for two or three months" a lie? Not really; there's a premise hidden here: the next pitfall is this one.

agreed to save for three months: continuous video recording and motion detection, resulting in a tenfold difference

the claim of "two or three months of storage" assumed to be motion detection recording, not continuous recording. One key difference: continuous recording is recorded continuously by the camera, whether or not there is a problem; Motion detection starts recording only when something moves in the screen, and stops when it stops. The two heads in my yard trigger over eighty times a day, recording one or two minutes each time, with less than 15% of the total effective recording time combined.

I switched all six heads to motion detection for a week, and the actual daily write volume fluctuated around 40GB. Still the same 2TB drive, with the storage period extended from 7 days straight to over 45 days. The "three months" number hasn't fully been fulfilled in my home because my yard has many trees and triggers too frequently. Families with low activity levels can indeed reach three months, which is exactly why it can't be generalized.

but there's one thing about the surveillance footage that I can't fully trust: the sensitivity is lowered, so moving objects don't trigger. A friend's electric scooter battery was stolen. Reviewing the footage, the thief pushed the cart step by step, rubbing along the footage. The surveillance didn't take it seriously at all, and in the end, the case was solved using continuous video footage from the neighbor's house. So my method is— continuously recording key safety locations, and only turning on detection inside the house. The three heads at the entrance and in the yard are always connected, while the three heads in the living room and dining room only have detection enabled, pushing the daily total to about 75G.

Recording After Internet Disconnection: The Three Methods Differ in Performance After Disconnection

this is the scenario most feared by people installing surveillance cameras: when you're out, the home broadband can't work, and the video is cut off. The answer depends on where the footage exists. How to restore broadband itself is another matter. Just follow the order of disconnecting the internet at home the usual order. Here, we'll only talk about video.

my home uses a NAS solution, with six POE switches connected to Feiniu's monitoring kit, and the recordings are written directly into a separately sliced disk. With this local storage architecture, even if the external network is disconnected, it still records because the entire route from the camera to the recorder goes through the internal network and never touches broadband. This is exactly the opposite of the previous post about not being able to see surveillance footage when going out the phone not being able to connect is a remote connection, but the home video recorder hasn't been delayed at all.

NVR VCR is similar; it also records over the internal network, and cutting off the external network does not affect the system. The real supply cut is pure cloud storage—the camera sends the recording to the manufacturer's server, which goes to the external network. If your home broadband is cut off, the cloud immediately runs out, unless you buy a 4G card model. There's another safety net worth adding to key locations: the camera has its own SD card. In extreme cases like a switch crashing or a cable being cut, you can still record your head to the local card for a while. SD cards can break quietly. I've suffered this before. the monitoring planning mentioned, check the card's status every month or two—don't assume it's always working.

want to store it longer, these three knobs are all on hand

the storage period wasn't enough, so there were only three places where I could twist it. I paid for it from small to large rows.

the first knob is the stream press. Dropping from 4Mbps to 2Mbps means storage is cut in half, but the video quality is slightly reduced, not a crash—2Mbps under H.265 encoding is enough to recognize people by face. My whole house is now 2Mbps. I tried 1Mbps on the front door, but the noise got noticeably higher at night, so I stopped adjusting it. By the way, if your head is still using the old H.264 code, switching to H.265 saves half the way in the big head.

second knob is for video recording, which is the continuous detection system mentioned above, with a tenfold difference. The only trade-off is the risk of missing a record, so don't apply it all—just sort by location.

The third knob is for adding and replacing a new disc. I replaced that old 2TB drive with a 4TB dedicated surveillance drive. At first, I thought about just using a regular drive taken from a computer, but I never dared—surveillance drives are a 7x24/7 continuous write load, and regular drives aren't designed for this intensity—the surveillance drives are. I've written a lot about the details of selecting a disc in the article how to choose a NAS hard drive, and the logic of surveillance drives is universal. One more reminder for those storing videos on a NAS: don't cram the videos, downloads, and albums into the same pool. Recording writing is nonstop and will wipe out all the sleeping opportunities on the drive. the storage pool is full of , you won't even know who did it. My approach is to set aside a separate disc and play only the video, so no one disturbs the other.

this setup, it runs about 75GB per day, and the 4TB drive can actually use 3.6TB, saving it for a month and a half. I accept this number—if you want to extend it to three months, you'll need a full-house surveillance scan. I don't dare bet that the head at the door missed recording. The gap between retention days and video reliability is a seesaw; everyone has to choose one side to press down.

find video and director video, I've fallen into both traps once

first pitfall: misaligned timestamps. One time, the package said it arrived but couldn't find it. I checked the video by the order time on my phone and kept scrolling back and forth, but that segment was missing. After fiddling for half an hour, I realized the camera at the entrance was 11 minutes slower than the standard time—NTP timekeeping was completely unequipped, and the camera drifted after running for too long. Later, I added the calibration server to the settings for each head, and set a habit of checking the time each quarter. This problem is similar to router timing mismatch it's from the same family: the device runs out of battery and relies on network timing to keep up. If the device drops to time, it drifts away. Before finding the footage, check the time in the upper right corner of the camera to save a lot of trouble.

second pitfall: export. A video was recorded in the mobile app, and the progress bar was so slow it felt like reminiscing about the 2G era—a few minutes of clips would take several times longer. To be in a hurry, I copied directly from the VCR: the NVR was inserted into a USB drive to export, and the NAS was dragged directly into file management—the speed difference was huge. If you really want to use the evidence clip, remember two points: import the original file, don't record the screen, and keep the watermark and timestamp; Export two copies, keep one for yourself. Looping overrides wait for no one; videos you think you "look back on" might be replaced by new footage next month.

Finally, here's the inspection order—just follow it: first, calculate how much your household writes per day based on the code stream and headers, then check the current disk and calculate how many days to store; If that's not enough, first reduce the bitrate and then check detection; only when you get to the bottom is it time to spend money to add to the market; Remember to use the timestamp after dubbing, and export important clips on the spot. With surveillance, how long the recordings are stored is never determined the moment you buy the hard drive; it's gradually extracted from these settings.