[mythtv-users] Where to dedicate processing power?

Anthony Vito anthony.vito at gmail.com
Wed Mar 8 03:03:14 UTC 2006

> Setup a RAID 5 array for recordings (since you'll have 4 tuners total you'll
> want the speed),

This is a common misconception around here. A high bandwidth mpeg2
stream in SD is only 8 M(bits)ps or about .8 M(bytes)ps 4 of them are
a mezzly 3.2 M(bytes)ps. Most modern harddrives can sustain 60
M(bytes)ps. So there isn't much of an issue here. It 'can' become a
problem when a few tuners are writing and a few tuners are reading. (
I would like to find some numbers on how many writing tuners and
reading frontends it takes to max out a single disk. ) I Assume you
didn't mean a hardware RAID 5 solution, and RAID 5 in software will
give about about the same performance as RAID 1 on the read, and much
lower performance on the write.

Back to the OP. Since this lad doesn't have much CPU power to begin
with, I'd suggest a single large disk. If you wish for redundency and
couldn't bear to lose recordings in a crash, or if the single disk
does become a bottle neck, get another identical disk and build a RAID
1. This can be done non-destructively and at any point in the future.

Also, I agree with a previous suggestion to keep the Tuner cards all
in one place, and in the same machine as the drives. This will further
reduce CPU usage and network traffic.

Anthony Vito
anthony.vito at gmail.com

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