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Date: Wed, 22 Jul 2015 01:32:18 +0100
From: Gary Palmer <gpalmer@freebsd.org>
To: javocado <javocado@gmail.com>
Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org>
Subject: Re: Prioritize resilvering priority
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References: <CAP1HOmTo28BishnEdPCBsg7V4M4yYfcSKw_AmUbPP-mW4JtRQg@mail.gmail.com>
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On Tue, Jul 21, 2015 at 04:06:05PM -0700, javocado wrote:
> Hi,
> 
> How does one go about prioritizing the resilvering process so it does not
> overwhelm normal disk I/O on a FreeBSD (8.3amd) system?  Further, can this
> be altered in real time, or do the settings have to be in place prior to
> the resilvering even starting?

You don't state, but is this on ZFS?

I assume they're on 8.3 also, but look at settings like
vfs.zfs.resilver_min_time_ms and vfs.zfs.resilver_delay in sysctl.
Searching for resilver_min_time_ms and resilver_delay may give
some hints, e.g. 

http://broken.net/uncategorized/zfs-performance-tuning-for-scrubs-and-resilvers/

does the opposite to what you want, but it should give hints.  Also

https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/zfs-advanced.html

I think they're dynamic.  I tuned the scrub settings and they took effect
immediately.

Regards,

Gary