The most live streams I have heard of on one server is about 100. RAM and CPU are the limiting factors, not bandwidth as with playback clients. We recommend a late model dual quad cpu, 8-16g ram, 64bit OS/Java, 1-4gbs nic and RAID 0 with as many disks as you can get (fast SSD drives are good)
To record many streams at once you should have RAID 0 or 1+0. Writing directly to NAS/SANS might work, but they would have to be close, otherwise consider using this to move recordings when they are done:
I'm not sure that the liverepeater system will be of much help. It is useful for scaling one or a few live streams to many clients. Will there be many clients? If the liverepeater is useful you should record on the origin. You can use StreamType "liverepeater-origin-record". If there is some good reason to record on a liverepeater edge, you can do it like this:
If a server crashes, and you are recording to NAS/SANS, and file is not corrupt (which is very possible in this scenario), and you are able to start and other server and write to same NAS/SANS location and stream name, then it should append. But that will be difficult to accomplish, there are a lot of "ifs"
There is not built-in equivalent on the edge. You could use the LiveStreamRecord API to start recording from the IMediaStreamActionNotify3.onPublish, which I think runs when edge starts re-streaming from an origin.