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Date:      Thu, 17 Jan 2019 05:35:05 +0000
From:      Steve O'Hara-Smith <steve@sohara.org>
To:        byrnejb@harte-lyne.ca
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Memory usage appears a bit high
Message-ID:  <20190117053505.cd2322c53eb451bfafb1f039@sohara.org>
In-Reply-To: <8f1f1f6c5532a9b076d878ff98a9044c.squirrel@webmail.harte-lyne.ca>
References:  <35c451bc1733004b7d868f60da68c639.squirrel@webmail.harte-lyne.ca> <20190116173621.9d90157c1adf526298763415@sohara.org> <0c45ab67b1480d39dd87059495f6a27c.squirrel@webmail.harte-lyne.ca> <20190116181146.375e2358d2091380c74a8291@sohara.org> <8f1f1f6c5532a9b076d878ff98a9044c.squirrel@webmail.harte-lyne.ca>

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On Wed, 16 Jan 2019 15:45:08 -0500
"James B. Byrne" <byrnejb@harte-lyne.ca> wrote:

> As I have never meddled with the sysctl settings on this bhyve host I
> infer that this setting in sysctl is calculated based on the total
> memory allocated when the vm is created:
> 
> vfs.zfs.arc_max: 3043799040

	Which is probably fine if the server isn't doing anything else that
demands much memory.

> How much should be committed to arc in a 4GB system?  What are the
> benefits / costs of more or less ram allocated to arc?

	The more RAM in the ARC the better the caching and therefore (with
a cache friendly workload) the faster the filesystem and the lower the rate
of wear on the drives. The downside - the ARC is wired so you need to
assess how much RAM the server needs for other tasks and throttle the ARC
to suit.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/



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