Real-Time Video Recording (ionice equivalent)

[Debacker]

Of course, just like you could put real-time processes in one CPU, and
normal processes on another to avoid implement complex algorithms.
While your solution is pragmatic, I would like to know if there are "clean"
ways to do it. If not, this would be a documented use case to why would
anyone actually need an I/O scheduler.

Laurent

On Tue, Jul 27, 2010 at 9:23 PM, Andrew Gould <andrewlylegould at gmail.com>wrote:

> 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
>