Dell POWEREDGE M1000E - Manual (Page 147)

Managing a Switch Stack 147
Default Stacking Values
Stacking is always enabled.
NSF is enabled by default. You can disable NSF in order to redirect the CPU
resources consumed by data checkpointing. Checkpointing only occurs when
a backup unit is elected, so there is no need to disable the NSF feature on a
standalone switch. When a new unit is added to the stack, the new unit takes
the configuration of the stack, including the NSF setting.