Real-Time Video Recording (ionice equivalent)

[Andrew Gould]

On Tue, Jul 27, 2010 at 1:45 PM, Debacker <debackerl at gmail.com> wrote:
> Hi,
>
> I'm looking for a ionice equivalent for FreeBSD. Let suppose that I setup a
> NAS using FreeBSD. I can substain 50MiB/s writing.
> Let suppose that I have a 720p security camera, writing at 2 MiB/s in a
> file. Then I have 10 users copying files around.
> All of this activity (camera + users) through Samba, so each connection has
> a dedicated process.
>
> Problem is that I want to give camera's maximal priority to guarantee smooth
> recording.
>
> I don't expect Samba to use much CPU, 99% should be spent in IO. So if I set
> the nice value of camera's process to Real-Time, it should do much, because
> its process will be on wait status most of the time.
> Consequently, when some IO requests coming from camera's process are in the
> queue, I want them to have top priority compared to requests coming from
> other processes.
> As the camera is limited to 2MiB/s, I expect the system to remain
> responsive.
>
> I know that seeks may lower the speed of the HDD, but as the HDD is slowing
> down, completing requests, I expect the number of camera IO requests to
> increase in the queue, and to be packed together, hopefully, stabilizing the
> number of seeks.
>
> BTW, I would use "root preexec" setting of Samba to execute a shell script
> for each new connection, giving best priority to the process if the user is
> "camera".
>
> Any idea?
>
> Thanks
>
> Laurent Debacker

Would putting the camera's storage space on a separate HDD from the
other users help?

Andrew