Strange slowdown when cache devices enabled in ZFS

[Daniel Kalchev]

On Apr 25, 2013, at 8:44 PM, Freddie Cash <fjwcash at gmail.com> wrote:

> Since these pools all have dedupe enabled, is it possible that the L2ARC
> feed thread searching the ARC for stuff to write to L2 is starving/blocking
> reads of the DDT from the L2ARC thus preventing the pool from writing any
> new data?

This seems very logical and would probably explain it. If your SSD is fast enough, there should be no reason to keep the default. I would guess that the "typical" (Sun's?) L2ARC SSD was very slow at writing and letting it do reads at the same time was awful.

But -- this might be a wrong track anyway -- do your dtraces :-)

Daniel