These monsters c2003 were triple glazed. Extremely heavy. There are two of them, meeting at the round corner column. Each one has three 'bays' i.e. two sliding leaves which both stack away to a third position. Also opening image on www.tomfosterarchitecture.co.uk.
They slide along the outside, boarded face of the external wall. They were by Hajom, now defunct, but using G-U hardware, can't find it on their current website but I remember
https://www.coastal-group.com/products/door-products/folding-and-straight-sliding-systems/HS-Portal-SCV
could supply, and this looks like it on this webpage.
Nowadays you can even make a pair of doorsets meet at the corner without a structural column or even a mullion, so the whole corner can disappear.

Posted By: richo106The supplier has said that our 6m sliding door would have to be double glazed due to size and weight and was unsure if the gearing would take the weight.

Plus, in addition to owlman's question ... what is the frame material, what is the gearing for? Is it purely a sliding door or is it lift-and-slide or something else? What is the airtightness rating? What is the thermal performance? (Brand and model name would be an easy answer! :)

Large glazed openings are either top hung or bottom rolling, occasionally, some firms do a combination of both.
The running gear for these systems is highly engineered and is very often a specific design, by a particular design and glazing firm as Mike1 indicated, so you end up having to accept their "full package deal".
The more generic running gear obtainable from architectural hardware companies usually isn't capable of taking extreme high loads. Also, that particular companies top and/or bottom load bearing tracks are an integral part of the overall package, and need designing in at the outset. I've seen some companies advertising loads of up to 400kg.
The specialist architectural glazing companies capable of designing and installing such systems aren't on every street corner.
Sorry if you've already been through all this.

If it is 6M, I'm guessing he'll need it motorised and a helluva crane.