Solved zdev questions and de-duplication memory requirements

[Phishfry]

I am still getting comfortable with my ZFS array of 2 zdevs of 8 drive raidz2. I am not sure 8 drive zdev are the best arrangment but these drives are older 512 Sector drives of 450GB size. (SEAGATE SLTN0450S5xnE010)

I am using my ZFS machine for backing up all my various FreeBSD machines. So it seems like De-duplication might be a good idea.
So my question is with 4.7TB of storage in my zpool would 64GB ECC RAM be sufficient to turn on Dedup? I am using compression as well.

One of the reasons that 8 drive vdevs worked so well is that all my controllers are 8 interface LSI cards. Is that reasonable?
The websites I learned from have lots of instances of 6 and 10 drive zdevs.

 

[Phishfry]

I am going to mark this solved.
Doing a whole lot of reading on dedup I decided to only use compression.
There may be benefits to dedup but I need to figure out other basics first, like snapshots and ZIL.

8 drive vdevs seem to be working fine I was just concernd it seemed that 8 disk vdevs are not recommended much.