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Ask the Expert: Understanding the requirements of video storage

Over the past few years, video storage costs have dropped dramatically — by 50 per cent per year — and compression techniques have improved vastly, providing organizations with far more choices in addressing their needs.

July 21, 2009  By Bob Moore

Three primary factors influence the amount of storage that your
customers need, including how you compress video, how many frames per
second are recorded (which may be different from what is viewed) and
the resolution that will be stored (there is no need to store the
entire image). Fortunately, several suppliers offer free online
“storage calculator” tools that enable you to plug in the three
variables and come up with a reasonable storage solution — and even
view how the video will appear.

Compression Standards
Compression plays a large role in determining requirements. For
example, a 1.3 megapixel network camera has four times the storage
requirements of a VGA camera. The good news is that H.264 offers vast
quality improvements, including 80 per cent network bandwidth and
storage savings, compared to Motion JPEG. The result is a more
cost-effective video surveillance system and simplified deployment and
management of large video surveillance deployments.

In real terms, the use of H.264 offers benefits in any one of three
areas. First, you can increase the video frame rate, even while using
existing bandwidth and storage capabilities. Second, you can increase
camera resolution to take advantage of megapixel capabilities without
having to increase bandwidth and storage requirements that would have
been necessary in the past. And finally, if you are satisfied with your
existing frame rates and resolution, you can simply reduce bandwidth
requirements, which may be important in wide-area network setups and in
cases where you want to reduce the storage costs of large archives.

Your storage requirements will also be influenced by the time period
that video must be stored. For example, high-resolution video shot at
30 frames per second may require a good deal of storage if it is to be
maintained for any length of time. And some organizations are bound by
regulatory requirements that insist that data be stored for three years
or more, such as our federal prison system or hospitals. In fact, there
are companies with over 40,000 terabytes of video storage.


Upgrade Considerations
It’s quite possible that your customers could find an analogue solution
that would meet its needs today. But to upgrade from a “black box” DVR
is far more difficult and expensive than IP storage. With a DVR, you’ll
be limited by the DVR’s upgrade limitations. It’s not always as simple
as opening up the box and changing or adding a hard drive. In some
cases, you’ll need to send the unit back to the manufacturer and pay a
premium price.
To avoid this, some companies simply buy three or four times more
storage for their DVR than needed. The problem with that approach is
that storage costs keep falling. So it is far more cost-effective to
buy additional storage when you need it.

A better choice is to go with a video management system (VMS) based on
open PC servers.  Even if a customer isn’t ready to fully upgrade to
network cameras, they can utilize video encoders with their analogue
cameras and avoid DVRs completely as an interim step. By choosing a VMS
over a DVR, hard drives can be added or replaced for as little as $150
per terabyte of storage.

Of course, there are several storage options available with a VMS and
the price for storage varies, depending upon whether you are using it
in a PC server or require more advanced capabilities. For example,
system storage can benefit from a redundant array of independent drives
(RAID), allowing users to easily replace drives in case of failure.
Arranging standard, off-the-shelf hard drives so that the operating
system sees them as one large logical hard disk increases storage
throughput as well as reliability. There are different levels of RAID —
from minimal spares to a full “hot swappable” mirrored solution where
there is no disruption to the operation of the system and no loss of
data in the event of a hard disk failure. RAID 5 systems may cost up to
$1,200 for a terabyte of storage. Don’t be afraid of quoting the higher
prices if a customer requires advanced capabilities.

Planning for Redundancies
Beyond using RAID capabilities for redundancy, you may store data in
remote locations. For example, I know of some large corporations,
correctional facilities, retailers and others that store data
simultaneously both onsite and in a central location. Others keep the
data local during the day and then move it to remote locations
overnight when network traffic and costs are lower.

One of the latest trends is to store data at edge devices — video
servers or network cameras in addition to other locations for
redundancy. In such cases, data is stored directly in memory cards. The
advantage of this approach is that storage costs are very low. The
disadvantage is that these edge devices are more easily stolen/damaged
and every two or three years memory cards need to be replaced. In
addition, few software companies have perfected the concept, so that if
you lose network connectivity, the VMS may not be able to properly sync
up the two storage locations. The technology will get there, because
there is a strong business case for the edge device approach, but it’s
not ready yet. Given all of the storage options described above, that
shouldn’t be an issue in finding an approach that meets your customers’

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