On 02/05/05 21:19, Brent Kilgore wrote:
So what is the max bandwidth of a typical system bus now a days anyway?Maximum (allowable) bandwidth for a DVD video stream is 9.6 megabits/sec = 9600 kilobits/sec = 9,600,000 bits/sec
And... what brand 120gb HD would you recommend. I would like to get 2
for less than $150. Unreasonable? Also, would a 5400rpm be ok or do I
need the 7200 to stream the video properly. Cache?
Maximum (theoretical) bandwidth available on a UDMA 100 IDE connection is 100 megabytes/sec = 800 megabits/sec =800,000 kilobits/sec = 800,000,000 bits/sec
I actually record at 2200 kilobits/sec (max 9600 kilobits/sec, variable bit rate--giving an average of about 2750 kilobits/sec). With NTSC video (and, although I haven't tested it myself, PAL video), you don't need anywhere near the upper limit available for DVD's.
In other words, even assuming you only get 1/3 of the max theoretical bandwidth of your IDE connection (which is a pretty accurate conservative estimate), you can fit a lot of MPEG streams onto that bus... You'll actually fill your PCI bus (with DMA traffic for the process of recording) long before filling the IDE bus.
I have a Myth box with 2 PVR-x50's and use 5400RPM UDMA100 drives (concatenated with LVM) without any problems. A friend has 4 PVR-250's and similar drives with no problems (even while recording 4 shows and watching a previously recorded show simultaneously). Neither of us paid more than $0.50/GB for a disk, so you shouldn't have any problems with 2x120GB for $150.
Remember, also, that rotational speed is only one (and definitely not the most important) of about 5 factors which determine hard drive throughput. Regardless, any hard drive you buy today will have far more capability than you need for MPEG2.
HTH.
Mike
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