Len Reed wrote:
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.
Thanks,
Len
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As people here have said, your system is pretty much right on for an
HDTV set up that could say, transcode at the same time as watching live
TV for instance. For just watching straight live TV or HDTV recordings,
as someone else said any fairly recent athlon64 variant (like a 3200+ as
you were thinking) would do. As to the question about more RAM, true
that in linux the ram you give it the more it can use and the more stuff
you can have open, unlike in windows with most of its applications.
However, if I was going to choose between one more gig of ram or going
from one to dual core, dual core would definitely win out. Mainly the
only performance increase you are gonna get is in the RAID (from the
benchmarks quoted in above post), but since you don't need anything
anywhere nearly close to that level of performance as you already knew,
the extra 1GB or RAM is pretty much wasting money. I don't know how I
could possibly get mythtv to actually fill up a gig of RAM at any rate.
Maybe a backend connected to 5 or so frontends?
Raphael
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