On Wed, 2007-11-07 at 10:39 -0700, Steve Lindemann wrote: > Mikkel L. Ellertson wrote: > > Steve Lindemann wrote: > >> In days gone by the rule of thumb for *nix was swap should be 1/2 the > >> size of RAM. Hadn't heard about that rule changing, but then I'm not on > >> the bleeding edge these days.... though on my servers with 16GB of RAM > >> it felt like a bit much setting swap to 8GB (but I did it anyway 8^) > >> > > I though the old rule was to for swap to be 2x RAM. This was because > > a core dump would use 1x RAM size of swap. This is no longer the > > case. Now days, if you are doing suspend to disk, you need slightly > > more then the amount of RAM in swap space, plus what you need for > > normal operation. If you are not going to suspend to disk, then the > > swap space needed depends on the system. If you have enough RAM, you > > do not need any swap space. For example, this system has 1M of RAM, > > and it normally uses more then 5M of swap space. There are no simple > > rules for swap size any more. > > > > The thing to remember is that swap space is used for when you do not > > have enough physical memory. It is sometime used for keeping > > program that are sleeping handy for reloading, but still freeing up > > RAM for other uses. (A program may get swapped out when more RAM is > > needed, and left swapped out even though there is RAM being used for > > buffers...) > > > > Mikkel > > > hhhmmm.... now that you mention it, I do remember way *way* back using > 2x RAM for swap. But we were lucky to a 1MB of RAM back then, 256K and > 512K was pretty common in the big servers. Somewhere along the way, as > RAM size increased, I picked up the 1/2 RAM rule of thumb (probably when > we passed the 1MB mark) and it's worked ok for me for some while now so > I pretty much forgot about the 2x rule of thumb. I wish I could blame > old age, but I've pretty much always had a rotten memory (probably could > use some swap space of my own 8^) ---- how to locate problematic memory banks... linux memtest86 Craig
