If all you built was a simple file server, it should not matter where you put the OS as what of the OS you need should be in memory post-boot. You disk access should be limited to read/write of the data being shared unless you built a file server with not enough RAM to hold the kernel and Samba in memory (and if you did that your data access is going to be absolutely horrible). In a heavy use file server, you want lots of RAM for I/O buffering and most likely a preference to low seek times on your drive configuration as most file access is read rather than write (with some exceptions). RAID1 should be ever-so-slightly faster than RAID0 for reading as RAID1 knows all data is on both drives. In RAID0, it has to spin some time determining which drive what data is on. In both cases, Linux's softRAID with perform split reads. RAID0 with offer faster writes as data is written 1/2 to each drive. RAID1 has to write all data to both drives. RAID0 is what you want for video editing. RAID10 (4 drives) if you want speed *and* redundancy.
--- As a footnote, RAID5 will not offer a large read performance boost over a single drive setup due to parity calculations. It may offer a slight write improvement as it takes less time to calculate parity and write some data to each drive than write all data to one/every drive. YMMV.