Good point, certainly true for progressive download. The worry is in case of streaming when the chunks of data need to be delivered simultaneously, unless the streaming server can do the trick?
Lelsaw On 3 May 2012, at 20:13, Hank Magnuski wrote: > Something doesn't seem right here. > > 100 viewers x 1 GB each requires a transfer of 100 GB in less than an hour. > > An ordinary SATA disk can easily do 100 MB/second so transferring 100 GB will > take 1000 seconds or 16 minutes. > > What's the disk going to do with the rest of the time? > > I'd say £100 is more like it. > > Hank > > On Thu, May 3, 2012 at 11:09 AM, Leslaw Zieleznik <[email protected]> > wrote: > > We have discussion today about the shared volume storage that can also > support streaming. > And the conclusion was that to support 100 streams (1GB/hour high resolution > recordings) played at the same time, > we need a high-performance disk RAID array which may cost at least £20k or > rather £50k. The calculation is shown below. > > Therefore my question is, whether there is any escape from purchasing such an > expensive storage? > > Many thanks, > Leslaw > > And here is the calculation. > Take the case of video encoded at 1GB/hour, equal to 300KB/s, stored on > a standard disk array with 4KB blocks. A single "viewer" will require > the disk to sustain 300/4 = 75 IOPS (I/O operations per second). > 100 streams served simultaneously will require 100 times as much I/O, i.e. > 7,500 IOPS. A typical 7200rpm disk can sustain at most 150 IOPS (i.e. two > streams); > a typical 5-disk RAID5 array (e.g. five 2TB 7200rpm disks) would support > perhaps 150*4 = 600 > IOPS i.e. just 8 streams! > So the solution is a high-performance RAID array. > > _______________________________________________ > Matterhorn-users mailing list > [email protected] > http://lists.opencastproject.org/mailman/listinfo/matterhorn-users Dr Leslaw Zieleznik OBIS (Oxford Brookes Information Solutions) Oxford Brookes University [email protected] Tel: +44 (0)1865 483973
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