Recommendation for a video editing file server

[AbdelrahmanSaid]

Hi guys. I am looking to buy a refurbished server for my home office to use as a storage for my live projects. I work as a video editor, and, up until now, I have been using either my local hard disk or USB 3.0 external disks as my working drives. However, my work has outgrown these disks, and I need to expand to a server that would be fast enough for accessing multiple HD and 4K videos.

I've got my eye on a DL-360 G8, but I have some questions before I go forward with the purchase:

1) There are two models available from the DL-360, the DL-360p and the DL-360e. What is the difference between both of them, and which one would better suit my needs?

2) When I contacted the reseller, I have got two different opinions regarding the hard disks I should use with the server. One guy said I should use the 3.5" SAS drives because they would be more reliable and, overall faster. Another said that both the 3.5" and the 2.5" should be the same. The opinions available on the internet and on other forums are mixed as well, so I am not sure which way to go.

3) If I go with the 2.5" drives, my current budget would only allow for the 3Gbps option. Reading online, I have seen some people claiming that the difference between 6Gbps and 3Gbps would not be noticeable in the case of a small server. Is that actually true? Would it be okay if I get these 3Gbps or should I try saving a bit more money and go with the 6Gbps?

4) If I go with the 3.5" drives, the DL-360p can only take four drives. Now, I don't want to install the OS on any of these drives, as I would like to have all of them as the file storage. I checked with the reseller and they said that there is no way for me to throw in an SSD with the OS. However, this unit comes with both USB and an SD card slot, and they said I can run the OS on one of them. I know that something like FreeNAS for instance can run on a USB, but I am a bit skeptical about the speed and the performance of the system. Also, I am more likely to use something like CentOS, rather than FreeNAS. Am I right in being skeptical about it, or should I just go ahead and install the OS on a USB or an SD card?

5) For the RAID, is it better to get the RAID controller that comes with the case, or should I drop it and go with software RAID?

6) Finally, which RAID configuration would be better for my needs? I know that RAID-0 would give me the maximum speed, but I know it is completely unsafe to use it. AFAIK, RAID-10 should theoretically give me the best read and write speed gain with room for 1 drive failure, but I would lose half the disk space. RAID-6, on the other hand, gives me more space, an option for 2 drive failure, but I don't gain as much on the read speed, and nothing on the write speed. For my use case, which way should I go? Keep in mind, that I am not intending to use the server as a backup, as I will be copying the projects to external hard disks to be safe, so I am more interested in having as much speed gain as possible, while of course still having some redundancy, just in case.