[CentOS] CentOS 7 and Areca ARC-1883I SAS controller: JBOD or not to JBOD?

> The disks I am going to use are 6TB Seagate Enterprise ST6000NM0034
> 7200rpm SAS/12Gbit 128 MB

Sorry to hear that, my experience is the Seagate brand has the shortest MTBF
of any disk I have ever used...

> If hardware RAID is preferred, the controller's cache could be updated
> to 4GB and I wonder how much performance gain this would give me?

Lots, especially with slower disks. You can also leverage write back caching 
if you have a battery on the controller as well. There are countless frameworks
and one off utilities that can properly report on the throughput for various
patterns, set it up both ways and know for sure.

Not related to your question, but something to keep in mind: What type of
enclosure are you using? If you are using an engineered system your enclosure
will communicate with the controller. When a disk fails it's a pain in the arse
to figure out where it exists physically. If you have an expander for example,
this gets even more challenging.

jlc