Date: Tue, 22 Jul 2014 13:35:41 -0400 From: Michael Powell <nightrecon@hotmail.com> To: freebsd-questions@freebsd.org Subject: Re: How much swap space for a 32 GB RAM system? Message-ID: <lqm7dg$vau$1@ger.gmane.org> References: <53CE8BB8.7030303@qeng-ho.org> <53CE8F62.8090701@tysdomain.com>
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Littlefield, Tyler wrote: > On 7/22/2014 12:05 PM, Arthur Chance wrote: >> I'm getting a new machine with 32 GB of memory. The old "twice >> physical memory" sizing seems ridiculous, so how big should I make >> swap? Do I even need swap with this much memory? >> > That number was always weird and never made much sense. What swap > ultimately comes down to though is you, the user. If you foresee needing > more than 32 gb ram, feel free to add more swap space. If you don't, > maybe 8 gb or so just to be on the safe side. If you really need 32 gb > swap space, I'd recommend just getting more ram, as that will be much, > much faster than thrashing. > HTH, The other consideration is crash dump. I run my servers without symbols, NO_PROFILE, and no kernel debugging stuff. Of course, should you actually run into a situation where you need to assist the devs troubleshooting you won't be able to do much. I use RELEASE branch(s), and only apply security updates so have an expected stability which I have seen in practice. From my viewpoint, if it works 100% when you initially setup a piece of hardware it will continue to work fine throughout the life cycle. Since I don't use such things (me sysadmin - not a coder) I'm not as knowledgeable, but I seem to recall that a crash dump needs a swap that is as large as physical memory. I think there is also a mini crash dump which does not. I would investigate the mini crash dump requirements to see if you can correlate some magic number from that - e.g., a box with 32G ram needs an 8G swap in order to do a mini crash dump kind of thing. At any rate having _some_ swap available is a Good Thing for a "just in case" scenario. It will buy you time to investigate and mitigate a runaway process. Other list members know more about this topic than I do, just wanted to point out the crash dump scenario. -Mike
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