Simon Billis wrote:
> John R Pierce sent a missive on 2010-04-12:
>
>> if this system is going to have 50 clients constantly playing videos
>> on it, then I'd look at 450gb or 600gb SAS drives, and a lot more of them.
>>
>
> I would look at the performance of the disk subsystem, make sure that the
> sustained read of the system is able to keep up with the demands of
> streaming video - you'll need to have 10K of 15K rpm disks for realtime
> video if you're streaming to a lot of users. It may be that their
> expectations are that the video isn't realtime and therefore you will be
> able to use slower disks and subsystem.
>
as he said it was a language lab, I'd expect at peak times, all 50
clients could be busy playing different videos. so, this disk system
has to be able to keep up with 50 different streams for extended periods
of time, which is a more complex workload than one faster stream. I'm
going to hazard a guess that most streaming video is under 1MByte/sec
but with 50 x 1Mbyte/sec playing at once, this becomes a more random
access workload than 1 x 50MB/sec.......
Also, there's a strong likelihood these language videos are somewhat
random access, and there will be a lot of seeking back and forth,
playing short snippets. Server-side and client-side caching will help
a lot on this but the requirement could well still be there. Response
time is fairly important here, if a user chooses to jump to a given
chapter, it should be accessible in less than 1 second or something.
frequent youtube style 5-10 second pauses for 'buffering' will result in
a lot of student frustration.
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