Appendix 1
Estimating HDD Capacity
The system currently supports 1TB HDDs. That may seem like a lot of space, though with
constant non-stop recording these gigabytes will be used up fairly quickly.
The task of estimating how many hours/minutes of recording time may be left on 500 MB of free
space may be a little tricky as well. That could seem irrelevant when you have the whole disc
space available, but as you realize you would like to view events from several weeks or months
ago, it quickly becomes relevant. The following formulas can help you feel more confident when
calculating the remaining disc space. Please also keep in mind that the utilized disk space may
depend on the video signal format, the video quality, the number of frames per second, and the
bit rate.
Calculating the capacity of the hard disk.
Timed Recording:
Step 1: Calculating maximum capacity of hard disk space for an hour of recording from a
given channel.
Assuming that S
ch
is the disk space needed for recording of an hour of live feed at the bit
rate of B (Kbit/s), the formula for calculating HDD space for an hour of recording would
be:
S
ch
= (B*3600) / (8*1024) = B * 0.439453125 MB
Step 2: Calculating the amount of HDD space (S
t
) needed for recording of T hours.
From previous calculation S
ch
is the disk space needed for 1 hour of recording. Then:
S
t
= T * S
ch
Step 3: To calculate how much of total disk space you’d need to record from as many
channels as you need, you will have to add up all the channels you will be using:
S
total
= S
ch1
+ S
ch2
+ … + S
n
For your convenience, you can use the approximate table below of HDD space needed for
recording an hour of video feed from one camera depending on video format, resolution,
frame rate and bit rate. For instance, on a 4 Channel DVR, at 768kbps bit rate, an hour
recording for 4 channels is 1.29GB, or a 500GB HDD can probably record for about 15
days (assuming some space is needed for system storage on the HDD).
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