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Date:      Sat, 20 Aug 2011 14:23:21 -0500
From:      Adam Vande More <amvandemore@gmail.com>
To:        Yuri <yuri@rawbw.com>
Cc:        FreeBSD Questions <freebsd-questions@freebsd.org>
Subject:   Re: How much memory does ZFS use?
Message-ID:  <CA+tpaK3qJ4fxNy=11GihbSRZjU6=c4jyq4p+wgXzzTjCvHbCPg@mail.gmail.com>
In-Reply-To: <4E4FFF23.406@rawbw.com>
References:  <4E4FFF23.406@rawbw.com>

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On Sat, Aug 20, 2011 at 1:38 PM, Yuri <yuri@rawbw.com> wrote:

> Someone told me that ZFS is a memory hog and it should be avoided as such.
> Is this true?
>

A rather ridiculous statement you were told and full of ignorance in my
opinion.  The 1908 Ford Model T got 25 MPG and my 2006 Mazda Speed6 gets
about 21 on the highway.  Which one would you rather drive around and
entrust with your family's safety?

Look at it this way, computer performance has increased very
rapidly(particularly in terms of CPU) over the last 30 years with one key
exception:  disk performance.  ZFS, among it's other benefits, does what it
can to mask this deficiency by offloading what it to more CPU and memory
intensive operations.  Offloading(where possible) slow disk to faster CPU
and memory resources which many server and desktops already have in abundant
excess is an excellent tradeoff IMO.

What difference does it make if it's a kernel module or not in terms of
memory usage?  Either way, set the appropriate tunable to control memory
usage and you're done.

vfs.zfs.arc_max="2048M"

-- 
Adam Vande More



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