Apropos the RD-180, Wikipedia writes to say
It features a dual-combustion chamber, dual-nozzle design and is fueled by a kerosene/liquid oxygen mixture
The RD-180 is really half an RD-170/RD-171 which has 4 combustion chambers.
For scale, here is an RD-180 with a person next to it. The RD-170 is basically the same size, just 4 instead of 2 thrust chambers.
The RD-17x family is vaguely in the same thrust class as the F-1. Combustion stability issues plagued the F-1 design, and took a lot of work to get going. With great success, in the end.
The Russians/Soviets did not have such success, and they took a short cut.
They were capable of building a turbo pump for a 1.5 Million lb thrust engine, but could not deliver a sufficient single thrust chamber. Thus the shortcut of one turbopump (or two, one for propellant other for oxidizer) feeding into 4 (or 2 in the case of the RD-180) chambers.
At a smaller scale, I think the RD-107 used on the Soyuz launcher is a much smaller engine, 183KLbs thrust that uses one set of turbo pumps and 4 thrust chambers.
And a RD-107A with a person next to it for scale.
You can see on the bottom of the Soyuz booster, that launches Soyuz/Progress spacecraft, what looks like 20 engines, but is realy 20 thrust chambers, and 5 engines.
Stability issues were much easier to resolve in many smaller chambers, than in one huge one.
Just for fun, compare the size of an F-1 engine (Which alas has good scale markers (people) but my other images do not really have them).
As a supplment to Geoffc's excellent answer, to address "Are more than 2 combustion chambers in an engine practical", the Bristol Siddeley Gamma 8 engine had eight combustion chambers. Black Arrow used it as it's single first stage engine
John Scott-Scott for scale:
