• 32-bit, 64-bit, and PAE, oh my!

The goal with this page is to sort out the variations of bitness and PAE on Xen servers and guests.

• At present (3.0.4), para-virtual guests will need to run at the same "bitness" as the Dom0, so you either use 64-bit all over, or 32-bit.

  • -Mats, in this post, among others.

  HVM is full virtualisation. PAE is the mode of x86-32 which supports large memory systems, non-PAE is limited at 4Gig of physical address space (which in practice means a bit less than 4Gig ram maximum). PAE and non-PAE are the standard ways of doing 32-bit guests (they support the same userspace, it's just the kernel that's different). If your guests are Xen-aware then they're not HVM. If they're running standard native installs and are fully virtualised, that's HVM. If you run xm info it'll tell you what kind of guests your hardware supports.

  • -Mark, in this post

  I'd say > 2 GB [RAM, then go with 64-bit], and I'd say if you are dealing with large files like DVD images, a true 64 bit register can handle the amount of data (=file size) more easily.

  • -Ulrich, in this post

Xen 3.0.4