What part does storage drive play in live tv functions

New user here, Received the dual lite unit yesterday. Initially ran it with no local storage and the live tv functioned well with a reasonable loading time of individual
channels. I found an older toshiba 320g drive in a usb enclosure and installed on the Tablo to try the recording function. Made a few recordings and tried them out this morning and they seemed to have worked ok. Tried live tv again and it was horrible. Endless buffering and a long time to load channels sometimes failing to load and when successful only played channels for a couple of minutes. Removed the toshiba drive and live tv is working fine again. What part does the storage drive play with live tv function?

The harddrive is used to provide pausing, rewinding and fast forwarding during live TV viewing. See discussion below.

I’m paraphrasing here, when “Cloud Storage” rolled out, the second generation tablo’s Dual Lite/64 has RAM capable to support live TV -

Before I discovered how to bookmark post, I believe either TabloTV TabloSupport explained the, well not exactly on board storage, but capable of buffering live TV for the newer line of DVRs.

Try a new USB HDD.