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Found the "limits" of my MythTV machine
http://forums.linhes.org/viewtopic.php?f=5&t=3656		 Page 1 of 1
Author:  nigelpearson [ Wed Feb 23, 2005 1:01 am ]
Post subject:  Found the "limits" of my MythTV machine
Last night, I finally found my performance limits. I was recording two DVB programmes, and watching another, while trying to burn a DVD using the mythburn scripts. It was going fine when replexing the files, transforming cutpoints, and preparing the DVD files (dvdauthor?) but when the disk started to burn, something had to give. The load jumped from about 5 or 6 to nearly 10.

It looks like the DVD recording was using just a little too much of the PCI/DMA bandwidth. The DVD seems to have recorded fine, but one recorded TV programme had lots of errors (MPEG2 glitches), and one is unwatchable (12 minutes long for an hour recording).

This is a cheap Gigabyte MB, Athlon XP 2400, two DVB cards and two HDs. I am amazed how well it coped with this much load, but am already wondering if a better motherboard might cope with more IO bandwidth.
Author:  yhan [ Wed Feb 23, 2005 9:41 am ]
Post subject: 
It might be too a too busy disk.

Personnaly I'm monitoring my box with nmon and Cacti.
I've a accurate idea of what my box is doing and when.

nmon is a tool from IBM for AIX at first, they compiled a version for Linux.
Just google to find it.

Cacti is a nice PHP interface around rrdtool (new version of MRTG).

If you are interessed of this tools, I can provide my scripts and give you a hand to setup it.

Yhan
Author:  nigelpearson [ Wed Feb 23, 2005 8:58 pm ]
Post subject: 
Thanks for the pointer to those tools - I had not heard of them.

I doubt is a "busy disk" issue. One IDE disk contains my /myth/tv, and one contains everything else. This means the backend was recording the two streams to disk A, playing back a stream from disk A, burning a DVD from files on disk B. The two disks are on one IDE bus, and the DVD writer is on the other one.

Short of buying a MB with three IDE controllers, or a better PCI bus architecture, I think this is the best that I can do. (except maybe a separate frontend/backend setup)
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