[Elphel-support] about data rates

[Sebastian Pichelhofer]

On Wed, Jun 13, 2012 at 11:04 PM, Carlos Padial
<palidoestudio2 at gmail.com> wrote:
> hi
>
> I have been using the camera at diferent sizes and compressions, and trying
> to find the limits (and looking at flavios article) i have some doubts...
>
> when recording to the hdd and streaming at the same time,(with same res as
> Flavio, 2064x896 what i call FMAX :)
> my limit is 240-250K framesize (at 25fps)
>
> when recording without streaming i can go up to 340K.
>
> I mean, when i pass this limmit the buffer overflow and there are (soon or
> later) dropped frames.
>
> just to be sure. My internal hdd has the same transfer speed as an external
> sata hdd?

yes

> are this values normal?

I was able to go a bit higher with SATA recording, if I remember
correctly I was able to go beyond 500KB per frame and reached a limit
at around 15-16 MB/s = 120 Mbit/s

> i collect some data from the hdd:
>
> hdparm -T -t /dev/hda1
>
> /dev/hda1:
> Timing buffer-cache reads:    44 MB in 0.51 seconds = 87681 kB/s
> Timing buffered disk reads:   43 MB in 3.02 seconds = 14537 kB/s
> [root at Elphel353 /root]3433# hdparm /dev/hda1
>
> /dev/hda1:
>  multcount      =  0 (off)
>  IO_support     =  0 (default 16-bit)
>  unmaskirq      =  0 (off)
>  using_dma      =  1 (on)
>  keepsettings   =  0 (off)
>  readonly       =  0 (off)
>  readahead      = 256 (on)
>  geometry       = 16383/255/63, sectors = 234441640, start = 8
>
>
> where can i find more info about the process running inside the camera?
> which one are necessary and which not when recording and streaming.

In the cameras system settings there is a process tab that gives a bit
of insight but there are not too many processes involved actually:

str = streamer
camogm = hdd recorder

all the other threads like 3 php instances, etc should be idling well
below 1% CPU usage if they are not used.
Please be aware that camogmgui does make a few PHP calls each second
to update the information it displays, so to get the absolute peak
datarate you would need to issue the camogm recording commands
manually over ssh/telnet.

Regards Sebastian

>
>
>
> best regards
>
> --
> Carlos Padial
> surreal.asturnazari.es
>
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