Storage Requirements for Video Playback
Proper planning is required when acquiring new storage for video playback. This is true whether it’s shared or stand-alone storage.
The three areas that need to be looked at are the transport, storage capacity and budget.
Transport or How Much Bandwidth1 Do You Need?
Let’s begin by considering using Ethernet (your LAN) for streaming video. A 1Gb. Ethernet connection has a theoretical limit of 125MB/sec. The real number we have experienced is 40-45MB/sec.; not even close. That’s a huge difference between what’s theoretical and what’s delivered. The same holds true for all of the other Ethernet speeds including 10GbE, 40GbE, 50GbE and 100GbE. You will need to figure out if Ethernet can even meet your overall throughput requirements. An experienced vendor will be able to help determine what works.
The first step in choosing storage is to determine how much storage space is needed and how fast your content can be written and retrieved. It’s all about the data rate2. For example, XDCAM EX’s 35Mb/s data-rate is actually only 4.5MB/s; however multiply that times the length in seconds of your video and the numbers start to rise dramatically. In fact, when we look at the numbers for a 4k RAW stream the data rate2 can be as much as 2.5GB/sec. Storage for delivery of these higher data rates2 is much more expensive, tends to be designed to include solid state disk and is generally part of a Fiber Channel SAN (storage area network). Very few vendors speak about this fact, however the motherboards of most computers cannot deliver more than one of these streams at a time no matter how fast the storage is.
You can generally find out video codec data rate2 requirements from the camera manufacturer or in many cases by typing in the question in the browser search bar. Once these numbers are determined, they can be added up to arrive at the total bandwidth1 needed for concurrent video stream playback.
Keep in mind the throughput requirement you come up with will determine the type of storage required (LAN or SAN).
Below are a few popular codecs examples and their related speeds for playback.
- AVCHD 1080p at 30 fps – 3MB/s
- XDCAM EX 1080p at 30 fps – 4.5MB/s
- ProRes 422 HQ 2k at 24 fps – 25MB/s
- REDCODE36 RAW 4K at 24 fps – 36MB/s
In general the faster you want to deliver video the more expensive it can get. Today there are many newer cameras delivering very high definition (4k for example) through newer codecs that do not require the original raw speeds. These newer codecs provide a compression algorithm which allows for lower playback speed and a smaller amount of storage. Even so, you need to do the math and consider how much content is to be stored on fast disk and how much nearline disk for quick access.
Let us help you to custom design a solution that meets your needs.
- Bandwidth: Bandwidth is the connection speed to the content. This connection controls your ability to retrieve and play back video.
- Data Rate: The Data rate (or bit rate) is the size of the video file per second of data, usually expressed in kilobits, megabits or megabytes per second.