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Date:      Fri, 29 Sep 2006 11:58:25 -0400
From:      John Nielsen <lists@jnielsen.net>
To:        freebsd-questions@freebsd.org
Cc:        Chris <snagit@cbpratt.prohosting.com>
Subject:   Re: Swap Size Importance?
Message-ID:  <200609291158.25518.lists@jnielsen.net>
In-Reply-To: <BAB82621-2B6E-4D53-9B0B-C7158E945E95@cbpratt.prohosting.com>
References:  <BAB82621-2B6E-4D53-9B0B-C7158E945E95@cbpratt.prohosting.com>

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On Friday 29 September 2006 11:52, Chris wrote:
> As a standard practice, I've always configured swap file to be double
> the size of real ram split across system and data disk. For example,
> 8gb on da0 and 8gb on da1 if the system has 8g real ram. In practice,
> In 7 or 8 years, I've never seen swap used for anything but a few k
> of inactive processes and I would imagine if real active process
> swapping occurred, it would be an immediate indicator that the system
> that isn't responsive enough for use anymore and requires upgrade or
> tuning. Can't run a website process off disk and keep anyone coming
> to the site ;-). (BTW, I'm talking only about high end servers, not
> test boxes where I've seen lots of swapping).
>
> I'm at the point of attempting my first gvinum software raid-5 and
> realized, I need the entire disk storage of all three non-system
> drives to avoid pulling an 8gb chunk out of the drive sizes. The
> configuration is one scsi 72g system disk and 3 that will be used for
> the raid volume. I should mention I turn off dumps, haven't found the
> use for that in a production server since it should not be rebooting
> or it's back in the shop and another box is taking it's place.
>
> Is there any shortfall in performance or reliability to running
> production with swap equal in size to the 8gb of system memory? I
> can't think of any but don't want to make a hard to correct mistake
> once this thing goes in.

Nope. I routinely run boxes with 512MB or 1GB of swap, even if the RAM size is 
much higher than that. You won't have anywhere to save a crashdump in that 
case, but you seem to already be aware of that.

JN



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