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Thread: Server Architecture on Rackspace

  1. #1
    Join Date
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    Default Server Architecture on Rackspace

    My company asked me to evaluate a possible server architecture hosted on rackspace to provide live one to many streaming services.
    The main idea is to provide a fully "on-demand" service to our customers: we'll use a wowza daily license model, and the same for rackspace infrastructure. So we need to instantiate the servers infrastructure every time a customer needs to setup a live event.

    I planned to use the origin/edge architecture to scale and the load balancing to determine which edge server has to serve the current client.

    I need to determine the optimal rackspace server configuration for both the origin transcoding/transrating server(s) and the edge servers, assuming that a single inbound stream will be 1280x720@30fps and has to be re-streamed at the same resolution to n clients.

    I'm currently evaluating these two configurations:
    - RAM: 15 GB - vCPUs: 6 - Disk Space: 620 GB (RAID10) - Public Network:200 Mbps - Internal Network:400 Mbps
    - RAM: 8 GB - vCPUs: 4 - Disk Space: 320 GB (RAID10) - Public Network:150 Mbps - Internal Network:300 Mbps

    For each of these two machines above I need to determine:
    - the number of inbound streams is capable to transcode
    - the "n" number of concurrent clients can serve if instantiated and configured as edge server

    About the number of transcodings I read this benchmark: Wowza-Transcoder-AddOn-Performance-Benchmark and assuming a 55% CPU max load, I can compare the "Server 4" mentioned in that benchmark with the 15GB Rackspace server above, so it can transcode only 1 stream at a time. Is it correct?

    What about the n concurrent clients in case the same 15GB machine is used to re-stream the live video mentioned above? Assuming an average bitrate of 1Mbps for each client and a 20% overhead: public network bw 200Mbps - 20% = 160Mbps corresponds to 160 concurrent users for each edge server. Is it correct?

    The idea is that this infrastructure has to scale dinamically instantiating a new edge server when the n number for the current server is going to be reached.
    Any advice/suggestion would be really appreciated.

  2. #2
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    Server #4 in the Transcoder benchmarks is an EC2 m1.xlarge, and does seem to roughly compare in ram and network throughput to your server spec. The m1.xlarge is known to have about 350mbs network throughput, and yours has 400mbs internally and you will be using internal bandwidth in this scenario.

    Re n concurrent clients, bandwidth is the usually the limiting factor.

    You can use the Load Balancer's serverInfoXML data as the basis for scaling. You might poll that data from your application server and launch new edge servers as needed. I don't know what rackspace provides for launching servers from your application.

    Richard

  3. #3
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    Thank you Richard for your reply.

    So bandwidth is the limiting factor also on the transcoding machine? I thought it was the CPU load, or at least this is what I understood from the benchmark I linked in my post.

    Rackspace provides a set of APIs to manage and control the VMs, but I have to investigate about it. I think we need something similar to the startup packages Wowza provides for Amazon EC2.

  4. #4
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    Maybe, but 400mbs is not much so that might still be the limiting factor, but I could be wrong. Might be CPU.

    Richard

  5. #5
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    Ok, thanks.

    But I must confess I'm a little bit confused. Could you explain how the transcoding addon process works? I assume there's a source live stream coming from outside to the transcoding server (so the bandwidth should be the public one)... and then? What happens?

  6. #6
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    External Encoder > Wowza Transcoder/Origin > Edge Server

    I don't have rackspace experience. I don't know how external vs internal network access is utilized.

    Richard

  7. #7
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    Thank you Richard.
    I'll do some tests and report here.

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