Date: Sat, 27 Apr 2013 10:49:09 +0300 From: Daniel Kalchev <daniel@digsys.bg> To: Freddie Cash <fjwcash@gmail.com> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org>, Andriy Gapon <avg@freebsd.org> Subject: Re: Strange slowdown when cache devices enabled in ZFS Message-ID: <6F1DCA37-9159-47F2-9ABB-FDEC41665611@digsys.bg> In-Reply-To: <CAOjFWZ60r5X_vP3g7vFXWZt0E1Vk-9KcTANVm9ReqfUUmvNqQg@mail.gmail.com> References: <CAOjFWZ6Q=Vs3P-kfGysLzSbw4CnfrJkMEka4AqfSrQJFZDP_qw@mail.gmail.com> <51430744.6020004@FreeBSD.org> <CAOjFWZ5e2t0Y_KOxm%2BGhX%2BzXNPfOXb8HKF4uU%2BQ%2BN5eWQqLtdg@mail.gmail.com> <51487CE1.5090703@FreeBSD.org> <CAOjFWZ6uL5nJ3X0Bz-oxJf-o21k81HfkR3PgwM022R4W21_5ZQ@mail.gmail.com> <CAOjFWZ60r5X_vP3g7vFXWZt0E1Vk-9KcTANVm9ReqfUUmvNqQg@mail.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=
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