ELRO FA420DVR 4-ch digital recorder + 500 gb hard disc USERS MANUAL - Manual (Page 73)

Page 73
Appendix 2. Hard Drive Capacity Calculation
When installing the DVR for the first time, make sure whether the DVR has internal hard drives
mounted. Pay attention to the jumper when installing an IDE hard disk;
1、
Hard disk capacity
The DVR sets no limit on hard disk capacity. Choose a disk 10G or more. For better
operation stability, we recommend the use of hard disks ranging from 120G~250G.
2、
Choose the aggregate capacity of the hard disks
Formula for calculating the capacity of a hard drive:
Total hard drive capacity
（
M
）
= number of channels × recording time desired (in Hours) × use of
disk space each hour (M/Hour)
Similarly, we can derive a formula for calculating recording time:
Recording Time (Hour) =
Total HD Capacity (M)
Use of disk space each hour (M/Hour) × number of channels
The DVR uses MPEG4/H.264 compression technology and has a wide dynamic range. When
calculating the hard disk capacity, it should use the estimated size of the files generated each hour
on each channel based on bit stream statistics.
For example:
Using a 500G hard drive and recording in real-time CIF quality can sustain approximately 25
days. Use of hard disk space per hour for recording on a single channel is 200M/Hour. When
recording 24 hours continuously in real-time CIF quality on 4 channels, the days it can last are:
500G/(200M/H X 24 hours X 4 channels) = 26.