In a 3000-square-meter logistics park in Baiyun District, 32-channel Hikvision surveillance (DS-2CD3T46 series 4 million bolt + DS-8632N-K8 NVR) began to "lose video" frequently in the middle of August: when monitoring, it was found that some channels were blank at certain times, or the screen repeatedly showed the prompt of "insufficient resources." The first reaction of the park administrator was that the NVR was aging and needed to be replaced, and asked us to evaluate the price of replacing a new 32-channel NVR.
Our conclusions after on-site testing:There is no problem with NVR. The problems are distributed in three layers-power supply, wiring and hard drive. It can't be solved by changing NVR for a penny.
Layer 1: PoE power supply is insufficient, camera is in "repeated restart"
The channels with lost videos are concentrated in No. 9 on the west side of the park. Log in to NVR to check the channel status. These 9 channels frequently appear "online-offline-online" records, each offline for 30 seconds to 2 minutes--the camera is repeatedly restarted.
Check power supply: 32-way camera is loaded by two 24-port PoE switches (each with a nominal PoE total power of 250W). The actual measurement shows that the switch on the west side is connected with 18-way guns with infrared supplementary light. When the infrared is fully open at night, the single-way power consumption is 8- 12W, and the total demand is 180W +. With two uplinks and one non-compliant PoE splitter, the actual peak value at night approaches the upper limit of 250W.Power budget critical, switch triggers overload protection, randomly cuts off some ports--Most of the cut lines are the longest and most power-consuming ones, so the ones lost are always fixed and concentrated at night.
Processing: Install an 8-port PoE switch (Haikang DS-3E 1310P-SI, RMB 480), divide the load of the west 9-way, and reduce the load rate of each switch to less than 60% after redistribution. The infrared is fully open that night, and there is no interruption.
Second layer: outdoor crystal head oxidation water, packet loss 30%
After the power supply is solved, there are 4 channels of occasional mosaic and temporary black screen. Ping these channels of camera IP, packet loss rate fluctuates between 12%-30%. Check the line: these 4 channels are outdoor points of the park gate and unloading platform, the crystal head is directly exposed outside the waterproof box, peel it open and have a look--Crystal head contact black green (oxidation), network cable skin cracking water.
The life killer of outdoor monitoring lines is water and ultraviolet rays. Treatment plan: all 4 outdoor lines are redone, and the integrated waterproof crystal head with silicone sealing ring is replaced. The network cable jacket is added with bellows, and the joint position is moved into the waterproof box and glued. After redoing, ping packet loss is 0%.
Layer 3:47 bad sectors of monitoring disk, write timeout causes "insufficient resources"
After the picture stabilizes, the NVR still occasionally pops up "insufficient resources, some videos are lost". This is not a network problem, but the NVR write disk cannot keep up. Go to the NVR hard drive management to check SMART: disk No.1 (West Digital Purple disk 4TB, WD42PURZ, has been in service for 4 years and 2 months)Number of reallocated sectors 47, sectors to be mapped 11.
Bad sectors disk write head to retry repeatedly, 32 channels of 4 million pixels of continuous write traffic about 45MB/s, bad sectors retry directly block the write queue, NVR can only discard part of the video frame — this is the truth of "insufficient resources".
Processing: Replace 2 pieces of Western Digital Purple Disk 6TB (WD63PURZ, monitoring dedicated disk, support 32-way write load, RMB 1050/block), there are 11 days of video on the old disk, we first mirror the export critical period (the week needed for the park theft dispute), and then retire the old disk.
List of costs and division of responsibilities
| Item | details | cost |
|---|---|---|
| Power supply rectification | 8-port PoE switch RMB 480 + line redistribution man-hour | RMB 680 |
| Outdoor line rectification | Waterproof crystal head ×8, bellows 30 meters, working hours 4 hours | RMB 960 |
| hard drive replacement | Western Digital Purple Disk 6TB×2 (2100 RMB)+ Video Migration Export + Man-hour | RMB 2600 |
| total | —— | $4,240 |
Compared with the 32-way new NVR scheme (machine RMB 5800 + installation and debugging RMB 1200 = RMB 7000, and do not solve the power supply and line problems, the video will be lost as usual), layered investigation saves nearly RMB 3000 for customers and really solves the problem.
Investigation sequence of missing surveillance video (by hit rate)
- First look at the NVR event log: Channel offline and offline records point to network/power supply,"insufficient resources" points to hard drive or code stream configuration, and recording plan error points to settings.
- Check SMART hard drive and video status: bad sectors, capacity is not full, cycle coverage, video plan is changed, three categories account for half of the lost video.
- ping each camera: packet loss >1% Check lines and crystal heads, intermittent on-off check PoE power supply.
- Focus on infrared time at nightPoE overload and power aging are concentrated in infrared exposure after opening.
- Consider NVR ontology last: NVR true bad performance is all channels abnormal at the same time or directly do not turn on, single channel, sub-period loss basically has nothing to do with NVR.
ACCPC undertakes Guangzhou CCTV system maintenance: 32 roads within the park/shop annual insurance RMB 3600–6000 (including quarterly inspection, joint maintenance, hard drive health monitoring, unlimited remote support, on-site man-hour fee free), single on-site inspection from RMB 300.