L2ARC

[alxxer]

I currently have 24TB raw storage, 12TB (stripped and mirrored) and 8GB ECC ram. Will I benefit by adding a 30GB PCIe as the L2ARC?

Thanks

 

[cyberjock]

L2ARCs consume RAM for the index. You shouldn't even be considering L2ARCs until you have maxed out your system RAM.

 

[alxxer]

My system, supports a max of 8 GB ram.

 

[titan_rw]

Is your systems typical workload random read io constrained? Even if it is, a 30G l2arc is going to use a few (2 or 3?) GB of ARC to keep track of what's in the l2arc. So your already ram constrained system is going to be even more constrained. Probably slowing it down overall. Worst case scenario is it's ram starved to the point of crashing the system. Zpool's have been known to be unmountable after crashes like that.

Even if you'd benefit from an l2arc (lots of random reads that the main pool can't supply), I wouldn't bother unless the system had at least 16GB of ram. 32 would be better.

 

[cyberjock]

You need to look at buying hardware that supports and has more RAM before anything else. 8GB is the minimum for ZFS. You're already walking a close line by having so little RAM for such a size pool. Don't push it over the cliff. You'll be very unhappy and regret your decisions.

 

[alxxer]

I build that system over 2 years ago, thinking of going with one of the supermicro M-ATX boards now with a sandy bridge CPU, they support 32gb of ECC ram.

Thanks