[mythtv-users] Draft revisions to HowTo section 3.3, second try

[Bruce Markey]

Ray Olszewski wrote:
> At 02:58 PM 4/23/2003 -0500, Kelly Reed Schuerman wrote:
> 
>> Just a comment on system requirements, in section 3.3.3 would it make 
>> sense
>> to discuss harddrive speeds and their relevance to system 
>> performance?  I've
>> had great success recording a show at 480x480 MPEG-4 while watching a
>> previously recorded show using an Athlon 650 with 256MB PC100 SDRAM.  I
>> believe the speed of my IDE channel and harddrive (UATA100, 7200RPM) 
>> has a
>> lot to do with that. I have recently put in a second tv tuner, reduced 
>> the
>> quality to 320x480 to compensate and I have been successful recording two
>> shows at once.
>>
>> Just thinking out loud...
> 
> 
> Saying *something* about this topic appeals to me. But ... what? Aside 
> from the fact that DMA support is a must, what do we as a group 
> concretely know about performance requirements for IDE drives? (For that 
> matter, does anyone here use SCSI? What are those of you who report 
> capturing to NFS mounts use?)
> 
> What rotational speeds, seek times, UDMA levels are needed? How much 
> does it matter if the live-buffer location is on a different physical 
> drive from the long-term-storage partition? If you use 2 drives, how 
> important is it that they be on different IDE channels?
> 
> Because hard drives for vidcap have to be big, they typically have to be 
> fairly new as well. My only actual vidcap experience is with drives that 
> are 7200 RPM, use UDMA133, and are les than 18 months old. I don't know 
> whether a 5200 RPM drive, or an UDMA33 drive, would work or not, and I 
> hesitate to say it would not given my lack of presonal knowledge. I have 
> guesses about the answers to some of the other questions I posed, but 
> guesses aren't answers, not for a HowTo, anyway.

I agree and I see this is often misunderstood. Realize that
there are 3600sec/hr so a 3.6GB/hr output file writes 1MB/sec.
Most myth users are writing less than 0.5MB/sec and in Kelly's
case, less than 200KB/sec.

Disk throughput doesn't matter. It is only the efficiency of
DMA and CPU time for IDE that will have an impact. However,
I have no idea of how to compare or benchmark these factors.
I do know that TiVo and ReplayTV hackers seek out 5400RPM disks
because they can easily write fast enough and they hope these
will run quieter and cooler.

--  bjm