HP ProLiant 1600 Video Streaming Technology - Page 24

ECG068/0798 WHITE PAPER (cont.) 2...4 High Capacity Disk Storage As a rule of thumb, MPEG-2 compressed video data takes about 1 GigaByte of storage per hour of video content. A dozen two-hour movies would therefore require about 24GB of disk storage. Therefore, an important characteristic of video servers is their ability to accommodate the highest capacity disk drives such as 9.1 or 18.1 GB. Important parameters to consider include the total number and type of internal drive bays-e.g., the ability to accommodate either 1" or 1.6" disk drives. It is also desirable to be able to expand the storage as the system grows through the use of external storage options using SCSI or Fibre Channel technology. To accommodate all of this disk storage it is also important that there be a sufficient number of PCI slots available for the appropriate disk drive controllers. High Sustainable Throughput The real-time nature of video demands that it be delivered to the network as a continuous high bit rate stream. As a result, the most critical resource in a video server is often the I/O bandwidth for providing a sustainable bit rate for multiple concurrent streams. This sustained throughput is usually measured as the average number of bits delivered per unit time. Since video content is generally stored on a rotating disk, this sustainable throughput is greatly influenced by disk rotation speed, disk array architecture, and disk I/O bus throughput. Video content may also be "striped" across multiple disks to improve performance as well as to provide redundancy. It is therefore important that the video server be capable of accommodating high speed drives when needed, as well as wide (32-bit minimum) and fast PCI busses and multiple disk arrays with controllers that support content striping. For example, wide Ultra SCSI-3 disk controllers provide a sustainable throughput of 40 MB/sec-twice that of Fast-Wide SCSI-2. For some applications, the availability of high rotation speed disks- e.g., 10,000 rpm-is also desirable for maximum performance. High Performance Network High quality broadcast video can be delivered at bit rates ranging from 3 Mbps to 30 Mbps. This generally requires a high bandwidth network such as 100 Mbps Ethernet connection or a highspeed ATM connection. It is important that the appropriate network interface cards (NICs) be available with highly tuned and thoroughly tested drivers to deliver continuous high bit rate packetized video streams over the network. Multiple CPUs Video servers tend to be more I/O intensive than compute-intensive. While they still need to have a relatively fast processor, they don't necessarily need the fastest CPU available. However, it is sometimes desirable, depending on the capabilities of the video server software, to provide dedicated processors to the "video pump" function. This can prevent other operating system tasks from stealing CPU time from the all-important real-time delivery of video. It can therefore be desirable to be able to expand the server to multiple processors as the system grows. Expandable System Memory For smooth delivery, the video server software may maintain multiple buffers in memory for each active video stream to keep data flowing smoothly over the network while the next block of video data is being retrieved from disk. It is therefore desirable to be able to expand the system memory appropriately as the system requirements grow to support more concurrent video streams. High Availability It may not be unusual for video servers to be on call to serve up video content at any time day or night to anywhere on the globe. This need for higher than normal system availability may impose