This technical article will provide information on Camera Grouping to record onto HDD within a Hikvision NVR. The max writing speed of HDD is typically 160 MB/s. It is recommended to only use 80%~90% of the writing speed of a HDD for long term reliability of HDDs.
If the dynamic writing speed exceeds 80%-90% of the writing speed then it is strongly recommended for the installer to group the HDD. This is a strong feature of Hikvision NVR that some inferior products do not offer.
As we mentioned before, the max writing speed of WD HDD is 160 MB/s. If we look at a 32 Channel NVR (e.g. Hikvision 7732NI-I4/16P) for example this has a incoming bandwidth of 256 MB/s. But the HDD writing speed is 160 MB/s. If we use a Hikvision 7732NI-I4/16P NVR and 25 x 4MP cameras, then each 4MP camera the default bitrate is 6 Mb/s on the main stream (25 x 6 MB/s = 150 MB/s). Important note: use surveillance rated hard drives for your CCTV security system.
The bitrate is dynamic so it is possible the HDD writing speed could exceed 160Mb/s, which could cause issues and given the recommendations of not exceeding 80%-90% of writing speed (128~144 MB/s) then it is recommended in this example to split the HDD into groups, so some cameras will write to one HDD and others to a second HDD. In the above example, it is recommended to set up 2 HDD groups and allocate 13 cameras for HDD group 1 and 12 cameras for HDD group 2.
If the HDD is not grouped, the footage from all the cameras will be written to 1 HDD at a time which has a maximum write speed of 160 Mb/S. But if the HDDs are split into two groups then using the example above, group 1 with 13 cameras have a total bandwidth of ≈ 78Mbps with a maximum write speed of 160 Mb/S and group 2 with 12 cameras have a total bandwidth of ≈ 72Mbps with a max. write speed of 160 Mb/S. On the Hikvision NVR, you can configure the HDDs and cameras into groups either via the local monitor (directly) on the NVR or via the iVMS-4200 software.
Setting up Hard Disk Group directly via the NVR
Step 1. Setting the NVR using the local monitor, the path should be from the NVR Menu, select “HDD” then select “Advanced”. First you should choose the “Group Mode“, then you can set which channel can record to which group.
Step 2. Then you can go to the “HDD” then “General” and if you have more than 2 HDDs, you can click the edit button and set the group number to assign the HDD to a group.
Setting up Hard Disk Group directly via the iVMS-4200
Step 1. Setting via the Hikvision iVMS-4200 software, first choose the HDD group, and then NVR will prompt to restart.
Step 2. Then you can set the group number when you tick the HDD and click the modify button, in this interface you can also set which channels are to be recorded to which group.