> From: opensolarisisdeadlongliveopensolaris
> Sent: Wednesday, August 01, 2012 2:08 PM
> L2ARC is a read cache.  Hence the "R" and "C" in "L2ARC."
> This means two major things:
> #1  Writes don't benefit,
> and
> #2  There's no way to load the whole DDT into the cache anyway.  So you're
> guaranteed to have performance degradation with the dedup.

In other words, the DDT is always written in rust (written in main pool).  You 
gain some performance by adding arc/l2arc/log devices, but it can only reduce 
the problem.  Not solved.

The problem would be solved if you could choose to dedicate an SSD mirror for 
DDT, and either allow the pool size to be limited by the amount of DDT storage 
available, or overflow into the main pool if the DDT device got full.
zfs-discuss mailing list

Reply via email to