[mythtv-users] Killer system or overkill?

Len Reed crunchyfrog at charter.net
Tue Dec 13 14:02:29 EST 2005

Grant Horning wrote:
> Let me clarify...
> 	Software RAID 5 will consume approx 20% cpu under a heavy I/O
> load. The disk performance will be very good but you must remember that
> cpu time is also very important. With dual cores, software raid 5 won't
> be a problem at all. With a single core, I would be worried about maxing
> out the cpu. You can see some benchmarks at
> http://www.chemistry.wustl.edu/~gelb/castle_raid.html
> Also, don't worry about the onboard raid chip. You wont be using it
> anyway. Linux has its own software raid. Try 'man md'. 

Thanks.  I said "software RAID" (and meant "md") so I'm not sure where 
anyone got the idea that I was considering on-board RAID.  I'm not.

I can't imagine why disk performance would be an issue.  A 10000 RPM 
disk used as a daily write cache surely is unnecessary -- even at HDTV 
rates this isn't a huge amount of bandwidth by modern disk drive 
standards.  I'm considering RAID5 so that losing a hard disk won't be 
fatal to the video library.

> My advice for a kick-ass system that will do more than just let you
> watch HDTV.
> 		Get dual cores
> 		Get 2GB ram (see benchmarks)
> 		Use software raid 5
> 		Get a case with great airflow + lots of power

Pretty much what I was considering except for RAM.  I'll look at the 
benchmarks, though; RAM's not all that expensive.
> I'm not sure if JFS or XFS perform the same as EXT3 or Reiser under RAID
> 5. That might be worth looking into. 

Unless there's a good reason not to, I'll use XFS.  I strongly prefer it 
to ext3 for mythtv recordings.


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