Mailinglist Archive: opensuse (794 mails)

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Re: [opensuse] Get an SSD just for swap?
On 29/11/17 14:12, Carlos E. R. wrote:
The rule of "twice the ram" was a Windows 3 rule. And it was a rule because a) we used as much swap as we could, because RAM was scarce and expensive, and b) the max swap the system allowed was twice the RAM.

Actually no. Windows doesn't swap!

I don't know the difference, but Windows pages, which is a completely different technique.

There is no such rule in Linux; simply use as much as you need.

And this "twice ram" predates Windows, let alone Windows 3.

Try running a *vanilla* early 2.4 series kernel with swap == ram. As soon as the system even *touches* swap IT WILL CRASH.

In Linux I have run machines with about 30 times SWAP/RAM ratio. It worked fine - albeit slowly, of course. Yes, that amount of swap was needed, there was a memory hole in YaST that ate ram when updating.

In this desktop machine the ratio is 3.

The rule is "use as much as you like", agreed. But in order to work *efficiently*, the traditional Unix swap algorithm *needs* twice ram. It's a fundamental quirk of how it works.


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