On Wed, 2007-07-25 at 16:06 +0800, [EMAIL PROTECTED] wrote: > 32 bit machines can't use more than 4G. Bigmem kernels fiddle and go partway > but to use more than 4G use 64 bit!
More specifically, the bigmem 32-bit kernel uses PAE to use RAM greater than 4GB. The bad news is that this doesn't increase the size of lowmem (a complicated topic, but basically the memory that can be used for disk I/O and networking). For some workloads this can be a problem because of the kernel's tendency to fragment lowmem (eg, backup servers are prone to this). That's the reason why it is better to use a 64-bit kernel. Of course, that has flow-on effects if you use bespoke or binary applications since you will need to recompile. Also, it can have an effect on your capacity planning -- 64bit applications usually need 25% more RAM. Of course, with as much RAM as you have you might be amply provisioned with RAM anyway. -- Glen Turner -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html