[geeks] Disk to Disk Caching

[Joshua D. Boyd]

On Mon, 2007-07-30 at 10:31 -0400, Sridhar Ayengar wrote:
> Joshua D. Boyd wrote:
> >> Ok.  I have this Lacie Firewire 800 external RAID 0 hard disk.  The 
> >> drive is just *barely* fast enough to stream compressed HD video. 
> > 
> > What compression are you using and at what bitrate?
> 
> I'm not sure of the bitrate.  I'd have to go check.  Some of the stuff 
> is MPEG-2 and some are VC-1.  All of it is in 1080p format.

1080p23.97, 1080p24, 1080p25, 1080p30, 1080p50, 1080p59.94, or 1080p60?

Assuming that you MPEG2 is coming from HDV, it shouldn't be any higher
than 25Mbit/second, which is a little over 3 megabytes a second.  I find
it difficult to believe that you FW800 disk array can't keep up with a
modest number of simultaneous FW800 streams.

Were you using XDCAM-HD, that goes up to 35Mbit/sec, but that is still
only 4.3MByte/sec.

Now, VC-1 can go up to 135Mbit/sec, which is nearly 17Mbit/sec, but even
two streams of that should easily be within the realm of doable for a
FW800 array (provided that it wasn't built using 7 year old disks).

Have you tried benching the transfer speed of the array to look for
malfunction there?