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Subject: Re: Strange slowdown when cache devices enabled in ZFS
From: Daniel Kalchev <daniel@digsys.bg>
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To: Freddie Cash <fjwcash@gmail.com>
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On Apr 25, 2013, at 8:44 PM, Freddie Cash <fjwcash@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=