[OpenIndiana-discuss] Swap during install

Richard Elling richard.elling at richardelling.com
Tue Sep 25 12:50:58 UTC 2012

On Sep 24, 2012, at 2:22 AM, Gabriele Bulfon <gbulfon at sonicle.com> wrote:

> Hi,
> I noticed that I usually have to grow the default swap installed by OI or XStreamOS, because the
> default text installer set up following some rules (stated inside the python sources):
> memory        type           required    size
> --------------------------------------------------
> 900mb-1G      zvol            no          0.5G (MIN_SWAP_SIZE)
> 1G-64G        zvol            no          (0.5G-32G) 1/2 of memory
> 64G          zvol            no          32G (MAX_SWAP_SIZE)
> I find these settings very limiting, as I remember being told for Solaris 10 to make swap double the available RAM (while here it keeps it half).
> What do you suggest?

Use what you need. Most people don't need or want to use swap. Why? Because...
if you have to swap, performance will suck. Period. Case closed. Game, set, match.
HDDs are 5 orders of magnitude slower than RAM and all the king's horses and all
the king's men can't fix that.

The old rule of "2x" RAM has not been true since around the time you could put 1GB of 
RAM into a machine. Interestingly, the place we normally see vehement arguments for
2x RAM is from Oracle DBAs who believe everything ever written in an Oracle manual :-)

hint: run "swap -l" and see if free == blocks. If so, then you've never used
swap since the system was booted.

illumos Day & ZFS Day, Oct 1-2, 2012 San Fransisco 
Richard.Elling at RichardElling.com

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