Cache file on ZFS volume or raw block device

Per Buer perbu at
Mon Apr 15 09:44:59 CEST 2013


On Sun, Apr 14, 2013 at 5:33 AM, Leif Pedersen <bilbo at> wrote:

> What do you guys think? Am I wasting my time, or is it worth the effort to
> avoid some filesystem overhead for cache IO? I thought that perhaps
> allowing the storage to be a raw block device might also be useful for some
> people (maybe my future self) who want to put it on a dedicated SSD.

We tried disabling those checks and running Varnish on raw Linux IO devices
a couple of years back. Not completely raw IO devices but those that still
keep the page cache active. The results where rather disappointing with a
significant reduction in performance. I guess the
more aggressive preemptive caching in the filesystem help out a bit more.

It is not a costly experiment to conduct. Go for it. The VM your playing
with is a totally different one.

 <> *Per Buer*
CEO | Varnish Software AS
Phone: +47 958 39 117 | Skype: per.buer
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