Well, there are two levels of fragmentation: logical and
physical. Within the SQL DBs, there would be logical and
that is normal SQL maintenance. I assume you mean
physical, meaning disk fragmentation at the OS level/disk
level.

I wouldn't do it while SQL Server was on, as it is moving
pages around. In theory, if you sized your DB correctly,
you shouldn't have much fragmentation at the OS/physical
layer, but mainly at the logical.
possible (safe) to defrag the array without losing or
corrupting data or db's?