Some math......
40 x 3MP samsung cameras at H264 main profile no smart codec = ~186-192 MBs peak ( round to 200 MBs for all I care)
Dell Poweredge 710xd - Intel C600 chip set with QPI, No losses, bottlenecks there to worry about 6/GT's
no problems here
Raid controller H710 PERC - Data transfer rate 6GB per sec per disk/port
No problems here either
All drives are 4TB
Write speed
Disks Sata- 7200rpm WD red NAS pro 202 MBs sustained ( not peak)
- 7200 rpm WD gold 182 MBs sustained ( not peak)
- 5400rpm Purple 150 MBs peak ( best guess about 90mbs sustained)
- 7200rpm Black (R 2.0 with 128 cache) 218 MBs sustained)
SAS- 7200 rpm WD Gold 182 MBs sustained ( not peak)
- 7200 rpm Segate Iron wolf 214 MBs sustained ( not peak)
- 7200 rpm HGST Ultrastar 7K4000 172 MBs Sustained( not peak)
Raid 6 vs raid 10
12 4TB drives just cause is more than 8,
Usable space Raid 6 -40TB, Raid 10- 24TB
Max raid write speeds across array Raid 6, 10
WD red - 1616 MBs, 2204 MBs
WD gold - 1456 MBs ,1986 MBs
WD Purple- 720 MBs , 982 MBs
WD Black - 1744 MBs , 2378 MBs
WD Gold SAS-1456 MBs , 1986 MBs
Seagate Ironwolf- 1712 MBs , 2335 MBs
HGST Ultrastar- 1376 MBs , 1876 MBs
subtract 200 MBs from any number above to see how much wiggle room you have.
final thoughts
7200rpm Sata drives have caught up to 7200rpm SAS drives in this day and age Unless you want an extra hefty warranty that comes with the SAS drives and the head ache that comes with it when you have to replace that drive with an exact one in a couple of years you will be fine with Sata drives for something Small like this. nice reliable Sata drives not cheap ones....
as for Raid 6 or 10. well that's up to you if you need more space and there is someone that looks/ takes care of this thing at least once a month- 3 months, then I would say raid6 shouldn't be a problem, if no one is going to look at this server until something happens between years then raid 10 is a better choice as your drive failure tolerance is greater with raid ten by about 4 drives.
Raid 6 more storage, 2 drive failure,
Raid 10 ~half of raid 6 storage, 6 drive failure.