[vdr] Re: Disk performance

[tobias.meyer-janson@sign-lang.uni-hamburg.de (Tobias Meyer-Janson)]

Tobias Meyer-Janson wrote:

> Axel Gruber <axelgruber3@gmx.de>  wrote:

> > But back to your question: Yes - a simple maxtor 80GB device is enough for
> > 3 Simultan Recording or 2 Recordings and one Playback. - No Problem
> 
> That's all I want. (At the moment. :-)
> 
> > You can check hd-Performance with "bonnie" - but be sure to set a big
> > Check-File sice.
> 
> I'll try it tomorrow.

And so I did:
First I realized that 3 simultan recordings or 2 recordings and one
playback are possible for my system. But Even if i have only one
playback I often have that artefacts in picture and sound (not
necessarily at the same time).

Andreas Roedl <flood@flood-net.de> wrote:

> As you can see my system writes 22 MB and reads 26 MB per second. 

bonnie -2 250 says that my system sequentially writes blocks with 8320
kB/s and reads so with 14368 kB/s.  I think that's slow, isn't it?
But I saw that Johannes' system has about similar values, so is it
normal or not?

Than I checked the HD configuration again with hdparm:
- MaxMultSect = 16 and option -m: 16
- -i: *udma5
- -a: readahead=8 (on)
- -u: unmasking = 0 (off)
- -c: I/OSupport = 0 (default 16bit)

To test it, I set readahead to 32 (16kB) and as expected the
block-read/write-performance (tested with bonnie) increased to 42148 out
and 33963 in.
Unfortunately this setting is not kept during restart, though I used the
hdparm -k option.
And I'm wondering if this is really important for vdr: I looked up in
dvbapi.c that the VIDBUFSIZE is 1 MB, so it should cache about 2s.

Then I used vdr with the new setting to play a movie and record another.
It worked but I could not notice any improvement. The sometimes
appearing artefacts was still there.
After a while - I did not touch the remote control and there was no
starting or ending of a timer recording - the playing stopped and so the
whole system. After 2min (so watchdog had its 60s) I tried to use
another console but there was no reaction from the system so I had to
restart it the hard way.

Any idea what's wrong with my system? Is it the disk performance? Is it
hardware or software?
Any hints to witch values if necesarry I should change buffer and/or
hdparm settings?
I think I had this problem since I started using vdr but what about the
performance of a nearly full HD (like Carsten wrote about "recording on
almost full hdd")? At the moment I have from time to time only 50-120min
left.


TMJ