Best performance for raspberry pi as a vdr platform?

[hlundberg]

Hi,
I've configured a pi with 2 dvb-t sticks, an Usb sata external drive and vdr. It actually works quite well, but some issues appear when mutiple (3 or more) recordings are active. Of course vdr itself puts a lot of load, but so does the SATA IO process as well.

Are there any ways to optimize the SATA IO? not higher speed but lower cpu consumption. I'm using ext4 on the sata disk, are there better options? big or small journal? fs options, etc?

experience, anyone...

[riklaunim]

HDD on USB2 is limited to the USB2 throughput. Around 24-25MB/s in one way.

[hlundberg]

right, but what could be done to achieve minimum cpu load? vdr reads and writes huge sequential files.

[riklaunim]

encoding signal to media file may be the cause of high CPU load. That USB dongle has to do some work too. Did you checked what exactly is causing the CPU usage (dongle playing, not playing but recording, copying some big file to /dev/null or other device) ?

[hlundberg]

Well,
there's not much to do about the dvb-sticks - they have a job to do. And yes it seems each stick doing recording adds about 20% cpu load, and then about 10% per additional recording from the same stick.

But I've seen the usb-storage process take quite a lot of cpu from time to time. As vdr recordings are quite big, sequential files, and actually the content criticality is low (If vdr crashes in the middle of a recording I will most like skip the whole file), I was mainly thinking if there was a filesystem (and options) that would allow big sequential writes big huge block sizes, and low cpu utilisation....