Luis - Misc Disk Questions

1. My first question is about ZIL and L2ARC

I have owncloud and samba running serving 15-20 people (usually 10-15 at same time). Lots of sync between windows PC's on the lan with lot of small files (one of the steel and concrete structure software we use creates up to 3000+ 1kb file per project folder)... The rest of the files varies between a couple of MB and some, just a few, can go up to 3-5GB.

Last time I said I had 4 or 6 new 30 GB SSD laying around, but I was mistaken. I have 4 new 60 GB SSD only.

I've been reading on the freeNAS manual and forum, and people say the L2ARC should not be bigger than 5x the ARC (since it uses ARC to store L2ARC checksums I guess) and always max the RAM before going L2ARC (already maxed), because if people use too much L2ARC it can decrease the server performance. I thought the ARC was the server RAM (minus 1 GB), but in the freeNAS GUI instead of 32 GB -1 GB = 31 GB, ARC says it is only 22.9 GB. So... if I should have a maximum L2ARC between 115 GB and 155 GB, witch means between 2 or 3 60 GB SSD's.

Also I read people with 12 GB RAM going for 300GB+ L2ARC and saying they got better performance.

What would you recommend? Can I use 2 or 3 SSD for L2ARC, will they be mirrored or striped (i'll be using freeNAS GUI)?

Should I use 1 of the SSD for ZIL since owncloud does a lot of simultaneously reads and writes?

2. Second question:
Is it possible or recommended to create a new pool on same server? Like I mentioned last, I have 16 HD slots on my case on 2 LSI HBA. Can I use the first 12 to my existing pool (for people to work on) and in the last 4 slots create a new pool with vdev raidz2 bigger disks just to backup the files on the first pool? Is this acceptable? Any other recommendations? Should I need L2ARC or ZIL for backup pool?

3. Third question (last)
In techsnap, a long long time ago, I heard Alan and Chris talking about backups (on a feedback question) that the guy took off an hard drive from the server, replaced it with a empty one, took it home and placed it on his home freeNAS server, so that after a few "disk trips" it would have the same pool on both sides and after that he could sync over the internet just the differences. How can this can be done. If I take one disk each week, I get 1 disk first, drop it on my home NAS and a week after that I would take another (with data 1 week apart) and it would restore everything? If I make a pool for backup with 4 disk vdev raidz2 how would this work out? And, can I reuse the same disks?

Thanks for your help and keep up with these great shows. And sorry for all these noob questions (and my poor english, I'm from Portugal), but it's kind of your fault because you placed the BSD itch on me and now I'm divided between BSD and linux and stuck with a lot of questions, and even more as I continue.