The article will briefly discuss the difference between HPE’s “Large Form Factor (LFF)” versus “Small Form Factor (SFF)” as it pertains to its rack mount server rails.
Large or small form factors are descriptions of the physical size of a server. LFF servers can accommodate larger size drives while SFF can handle smaller drives, i.e. 3.5″ and 2.5″ drives, respectively.
Since HP LFF servers are physically larger than SFF servers, it would be logical that LFF server rails are larger than SFF server rails. This is true. However, it should be noted that SFF and LFF server rails will work with SFF or LFF servers. The important distinction between LFF versus SFF is that LFF server rails are set back a couple of inches.
In sum, LFF and SFF server rails should be used with their respective LFF and SFF servers. Otherwise, your servers will not appear flush with your other servers. If you install a SFF server in LFF server rails, your server would appear set back further than normal. And if you install a LFF in a SFF server rails, your server will appear to be set forward a couple of inches and you may not be able to close your rack cabinet door.