justin randell <justin.rand...@gmail.com> writes: > On 1 November 2010 09:16, Daniel Pittman <dan...@rimspace.net> wrote: >> >>>> Are there different types or levels of hardware virtualization available >>>> off the shelf, or it is one-size-fits-all? >>> >>> Well there’s Intel VT-x and there’s AMD-V, which are the duopoly’s >>> equivalents. Both are supported by VirtualBox, VMware, KVM, etc. >>> >>> Personally, I think that if you buy a new PC with hardware virtualisation, >>> the performance benefit you will see will be coming from the faster hardware >>> more than the VT-x/AMD-V support. >> >> *nod* Also, keep in mind that one of the biggest factors in VM performance >> is >> going to be I/O for most users. >> >> That means that the performance of your paravirtualized devices is the key >> for >> getting better performance - and that usually just means picking a VM >> solution >> with appropriate "guest" drivers and all. >> >> (Unless you plan on mapping physical hardware into the VM, in which case VT-d >> or the AMD equivalent makes a difference.) > > yep, I/O is normally a killer. at work, all dev machines have (at least) two > physical drives, so VMs can be given a disc separate from the host OS. we > find that's the simplest, best bang-for-buck way to get good VM performance.
Only if you have PV disk drivers - performance with the emulated hardware, even SAS and SCSI controllers, is generally way lower than the PV stuff because of the overheads of emulation.[1] FWIW, using KVM we reproduced the widely reported "native performance" using direct I/O and an LVM slice results; those later should work for any raw block device, not just LVM. (Which matches your comment, of course. :) Daniel Footnotes: [1] Really good non-PV drivers and good hardware can reduce it to the equivalent of only a few transitions into kernel mode, but they can't be as efficient as the "one or less" that PV drivers manage. -- ✣ Daniel Pittman ✉ dan...@rimspace.net ☎ +61 401 155 707 ♽ made with 100 percent post-consumer electrons -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html