Hello, welcome, great questions.
I believe you will really get some use out of that processor if you can keep it cool. Do you have the vga adapter so you can see to install the OS and tweak the bios to turn the fans up? Unless you live in a cooler part of the world, that cpu will get pretty warm, if you use hot drives with it, it will make it worse, might want to think about using the WD red drives, they run about 10-15F degrees cooler then normal drives. With ssd for the os, I don't notice the slower speed on the reds.
As far as running win2012E on a 490, I have done it with cpu and ram upgrade, it ran ok on 2 mirrored ssd drives.
While we had drivers and programs to get whs 2011 lights to half way work, I never could get the same files to work with the lights on win2012E. So I ended up building a DIY and placing 2012E on it. Doesn't mean it can't be done, but it has been some years and may be hard to find all the files needed and it may still not work.
I really didn't mind blinking lights because of the SMART program (paid) that kept an eye on the drives.
http://www.dojonorthsoftware.net/ worth every dollar.
As far as drive pooling software, I first purchased DriveBender which seemed to work, but on the recommendation from a friend I purchased Stablebit Drivepool and that is what I use now. It is very easy to install and use and if you pull the pool and place it in something else, the pool will still be there, very durable.
It allows you to pick how many copies of each file on however many drives you have, I picked 3 copies to be on the safe side on 4 drives.
Hope this helps, Good silver cpu paste, speeding up the fans, using drivepool and smart and I believe you will enjoy the mini server.
I always encourage people to go to ebay and try to find a decent priced backup (like) server just in case.
The trays all fit, the power supplies all fit, most everything makes for spare parts which HP does not sell. Something to think about long term unless you decide to build something if/when it fails.
My DIY is in the DIY thread and many others are in their as well if you decide to go down that road, they have some pretty cool MITX motherboards and cases that have plenty of bays for drives now days. Plus the extra ram let me run a win7 VM on mine for a HTPC in the same box.
Good Luck, hope this helps and enjoy.
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[X510 CPU/RAM/
All 2 TB Red's] [X510 CPU/Sync'ed Backup/All 2 TB Hitachi's]
[X510 /2 in box]
[X710 LIAN LI DIY W2016E] Stablebit Drivepool [EX-503 LIAN LI 5-bay USB3 External]
Fear the Cloud