Ten Tips for Choosing a Streaming Server

Tip Six
If you are a mixed Windows and Linux shop (or looking to upgrade to Linux), consider Real’s Helix Universal Server software. The value of Real’s software is that it supports all the major players—WMP, QuickTime, and Real’s own, as well as MPEG-4. Plus, it runs on Windows or Linux.

The price for Helix varies based on your throughput requirements. It can be as little as $4,000 or as much as $40,000 for unlimited bandwidth. There’s also a free version, but it only supports Real format and is limited to five streams.

Real has done a good job of leveraging even entry-level hardware to run with Helix. Real claims that Helix can serve up 1,000 clients on just 768MB RAM and a 500MHz processor. So although there’s a licensing cost for Helix, it can be balanced against its lower hardware requirements to keep on budget. Even so, Helix performs at the top of its class in industry tests for streaming servers.

Tip Seven
Purchase a RAID subsystem for storing the video content.

Internal server storage may seem adequate now, but the reality is that content balloons geometrically. So in your search for a new media server, plan now to include a subsystem and controller along with the internal storage and embedded controller. It will make upgrading and increasing storage much simpler. The other benefit is that dedicated video storage will improve throughput.

In the past, we would have recommended using a RAID 3 configuration for video content over RAID 5. RAID 5 has more overhead than RAID 3 and is tailored to perform better for smaller database file access than for the larger, continuous reads of video content. Now, with improved hardware and software, RAID 5 runs nearly as well as RAID 3. Since most systems offer a pre-configured RAID 5 option, choosing this will save the hassle of generating or reformatting the set later on for RAID 3.

Look for a RAID controller card supporting PCI-Express x16 or PCI-X (especially 2.0 and above). Either of these provides significant advantages for throughput. Also, look for a disk controller with at least 64MB of read cache onboard (or more). This will provide sufficient throughput to overcome any RAID overhead. You may have to ask about this, as most vendors focus on write caching and protection via cache battery backup. For streaming, it is the read performance that we care about.

Finally, if you’ve opted for an Xserve as your streaming server, you can (and should) upgrade to the Xserve RAID subsystem. The 1TB version goes for $6,000 and includes a PCI-X Fiber Channel card.

Tip Eight
Do you want or need MPEG-2 for internal use? Consider an SGI/Kasenna system. If absolute top quality and performance are issues, look to the Kasenna software/SGI hardware combination. Kasenna’s MediaBase XMP software is a true, carrier-class VOD solution for MPEG-2.

Running on an SGI Origin 300 server, MediaBase could readily handle a community cable TV system with VOD, let alone a corporate training or classroom environment. Of course, this is high end, about $200 per stream or more, for a product intending to handle 1,000 or more simultaneous users. But for making MPEG-2 content available, there’s no better way to go.

Tip Nine
If the highly cost-effective Xserve won’t fit your needs (such as in an all-Windows shop), consider using a high-end gaming PC as the basis for your server.

Many vendors today offer such systems—both white box and brand name. These systems are pre-configured with both the processing power and throughput needed for streaming media service.

For example, Dell offers their XPS Gen 4 system with internal RAID SATA storage, up to 4GB of RAM, and an Intel Pentium 4 Extreme Edition for under $4,000. (A more typical rackmount video server might run about $7,500.)

Tip Ten
Remember the four key elements to an effective streaming server: CMAD.

Let’s suppose that a Gaming PC won’t go over with the powers that be when it comes time to secure funding for the new server. You’ll need to consider what specifications are essential for a system from any of the various hardware vendors. There are four major potential bottlenecks for streaming media servers you’ll need to plan for in choosing your server. You can remember these using the acronym "Can Make A Dollar" (CMAD):
• CPU
• Memory
• Available Bandwidth
• Disk Throughput

Each of these elements impacts performance, and they all need to be balanced against one another. Rather than explore the minutiae of each component, here’s a rule of thumb for servers based on what many streaming host companies use:
• Intel Xeon processor 2.8GHz
• 2GB or more of RAM
• 64-bit PCI-X RAID controller
• Ultra320 SCSI RAID subsystem

While hosting needs are far greater than most in-house systems can support, the cost of purchasing most of this hardware is nominal today. Again, for around $4,500 you can get an AMD Athlon 64 FX-55 server with 2GB of PC3200 RAM. (Add about $4,000 for the subsystem.)

Note that while many suppliers of streaming media servers use Intel Xeon processors, the AMD Opteron or Athlon 64 are every bit as capable and do a better job of handling legacy x86 code.

Also, because of the nature of streaming sessions, dual- or multiple-processor systems do not increase performance significantly. For example, in one test, one processor handled 2,000 sessions while two handled only 2,600.

Available bandwidth is an issue for both internal and external streaming. No amount of server optimization can overcome limited bandwidth. Internally, count on having about 70-75% of the rated bandwidth of your Ethernet network. So, for example, a 100BaseT Ethernet would deliver about 70-75Mbps total. While it is common for a server to have a Gigabit Ethernet connection to switches, it is less common to find workstations with GigE. GigEther would deliver about 700-750Mbps.

For external streaming, look for a DS-3 or better (preferably an OC-3 connection). These are pricey, but even the finest server can’t pump data through a "soda straw" T1 line. Also, set appropriate expectations if your internal network includes wireless connections. Standard WiFi systems offer only about a tenth of the throughput of wired Ethernet networks. While this may be enough for office work and email, it is not enough for multiple video streams. If wireless connectivity is critical, consider upgrading to 802.11g access points and cards, which offer about a 3-5X improvement in throughput over 802.11b. Even then, you will need to limit the number of users trying to access video content through that router.

We mentioned a bit about disk throughput in Tip Seven. Avoid crowding video data unto the server’s own hard disk. Improve throughput with a PCI-X (or even PCIe x 16) RAID controller over an embedded one. Finally, use a good, 7200RPM RAID subsystem with redundant power supplies to keep things rolling.