[TriLUG] SWAP and SSD vs HDD

[Leonard Boyle]

please take a look at this you tube video from the linux.conf.au from 2014

It is one of the best write ups of a reason to have swap on linux.

https://www.youtube.com/watch?v=fNcdBQ-ANkQ

several points

- linux and most other o/s's will max out memory use for cache. So if
things get tight they normally can either release the used pages or swap
pages out.
- having pages swapped out does not mean that a system is doing heavy i/o
to the swap space. it might, but the system may have processes that are
long running but dormant.



Which is a little different then solaris or hp/ux. Solaris will reserve
space in swap when a process is started, to make sure that it has space to
swap out the process if things get really tight.

I  asked a red hat dev manager if linux reserved swap space on process
start up  and he said that linux did not.


On Thu, Nov 6, 2014 at 9:53 AM, Roger <RogerB at bronord.com> wrote:

> Linux does a great job of memory management. I seem to recall 8 GB of ram
> so, except in the case of very heavy usage, swap it's used very little.
> Monitor it and look at swap usage. The only time I saw maxing out ram and
> swap usage was with Windows as a guest in a Vbox VM because I pushed the
> limits on a laptop with 2 GB ram. When I closed Windows, swap usage dropped
> to near zero and ram usage dropped back to "normal." Even with multiple
> memory intensive tasks running, little swap usage, e.g., firefox +
> thunderbird + open office + GIMP.
>
> Given you'll likely see minimal swapping, "wear" of the SSD should not be
> an issue. Only good reason to put it there may be faster resumes from
> suspend.
> -- Roger Broseus
>     www.bronord.com
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