Stephen Harris wrote: > On Wed, Oct 29, 2008 at 09:56:34AM -0400, James B. Byrne wrote: >> I believe that the current recommendation is 2 x physical memory up to 2 >> GB and then 1 x physical memory thereafter. >> >> See: >> http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.2/html/Deployment_Guide/s1-swap-what-is.html >> >> " Swap should equal 2x physical RAM for up to 2 GB of physical RAM, and >> then an additional 1x physical RAM for any amount above 2 GB, but never >> less than 32 MB. > > That's a silly recommendation, and never been true for Linux. RedHat > don't always know what they're talking about. > > In older BSD systems (eg around SunOS 4 times or before) swap space was > utilised oddly; all memory was allocated from swap, so you needed _at > least_ <physmem> of swap just to use all your real memory! So if you > added <physmem> of swap then your total virtual memory size was still > only <physmem>. No help! So the rule of thumb came along that said > "swap = 2*<physmem>" and that gave you a VM of 2*<physmem>. Linux never > did this (and I don't think modern BSDs do, either) so adding <physmem> > of swap will automatically give you twice <physmem> of VM. Ah, yes, not an older release of Solaris...SunOS4 A certain release of SunOS4 required swap be twice the amount of RAM or it would crash according to an article that I read but I cannot find right now. Here is a FAQ article related to SunOS that tells us how SunOS4 handled virtual memory (swap must be at least the same amount of RAM): http://www.bjnet.edu.cn/sun-admin/FAQ/F-comp-sys-sun/Q30-0.html The source of this 'recommendation' that swap be twice that of RAM is affects more than just Linux http://blogs.sun.com/jimlaurent/entry/solaris_faq_myths_and_facts So please, stop spreading this swap should be twice the amount of RAM installed nonsense. /me gets off soapbox.