Date: Tue, 27 Jul 2010 20:45:34 +0200 From: Debacker <debackerl@gmail.com> To: freebsd-questions@freebsd.org Subject: Real-Time Video Recording (ionice equivalent) Message-ID: <AANLkTinqwCSzoCdEnrSoXN1jkpoIGmESgbMsI3JFB5YF@mail.gmail.com>
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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
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