The only time I notice any kind of slowdown with these drives (both of them in the MythTV backend for videos/recordings) is when mass-copying video files (multi-GB each) to them over the GigE LAN. After the first few GB, things slow down due to the slow sustained write/rewrite cycles.

My BE has only two tuners now, and there's no problem there.

In the past, I did test limits of MythTV with a 6-tuner setup, and got the system to record 8 programs (some digital channels have more than one "sub-channel") at once, whilst watching an older HD recording. Glitch-free.

The kicker though.. I did all of that using a single USB2 drive for the recordings. So data rates weren't really an issue at the time.

The MythTV backend code is good about using fdatasync() to prevent the uncommitted writes from piling up prior to the next (every 5-sec by default) kernel-initiated flush.

Cheers