This seems like such an obvious tool to me I'm surprised I am having
trouble finding something to do what I want to do.

We are using a Window server (2003 SBS cause it is what we have) with
a large drive for archiving live video from a network of about 30 IP
video cameras placed all around our business. These cameras can write
to an SD card or a NAS drive. When they use an SD card they
automatically rotate the oldest files out as the card fills up so that
at any given time the SD card will be full of the latest video files
going back as far as it has space for.

We want to use a file server instead so that we have all the video
files in one place and they are easier to get to. Problem is, I can't
seem to find a tool that will automatically maintain available disk
space on the video archive drive between a high-water and low-water
mark so that there is always space for the cameras to write the active
video stream.

Basically, the tool would check every 10 minutes or hour or whatever
(configurable) to see if the available disk space was below the high-
water mark (like less than 5% disk space available, again
configurable) and if so, delete the oldest files on that drive until
the low-water mark of disk space (like 10%, again configurable) was
free again.

Anyone know of something like this or do I have to dust off my rusty
scripting skills and write one myself?