At the RedHat Summit a couple of weeks ago, RH said that with a switch from Xen to KVM and lots of tuning, they were able to get the I/O overhead down to 5%. I thought that was pretty impressive. They also introduced a new product RedHat Enterprise Virtualization, which is supposed to support process migration and all the other niceties that we've come to expect from virtualization. I haven't played with it yet, but it sounds quite interesting.
I'd be interested to hear of anyone else's experiences with these. David On 9/16/2009 5:34 AM, Tim Cutts wrote: > > On 16 Sep 2009, at 8:23 am, Alan Ward wrote: > >> >> I have been working quite a lot with VBox, mostly for server stuff. I >> agree it can be quite impressive, and has some nice features (e.g. do >> not stop a machine, sleep it - and wake up pretty fast). >> >> On the other hand, we found that anything that has to do with disk >> access is pretty slow, specially when working with a local disk image >> file. > > I think that's pretty standard for most virtualisation, whichever > vendor it comes from. The I/O is fairly sub-optimal. I've had a fair > bit of experience now of various VMware flavours. The I/O performance > of the desktop versions is fairly shocking; this is presumably largely > down to the fact that desktops and laptops tend to have fairly slow > I/O to start with, and the virtualisation penalty is very noticeable. > > Our production virtualisation system uses dual-fabric SAN-attached > storage (EVA5000), ESX 4.0 as the hypervisor, and we're running about > 20 virtual machines per physical host. Most of these applications are > not I/O heavy, but really trivial benchmarking using hdparm indicates > I/O bandwidth within the VM of about half that if the machine were > physical. Very unscientific test, though. I should do some proper > testing with bonnie++... > > Virtual disk performance in ESX 4.0 definitely feels better than ESX > 3.5, but that's largely because they've got rid of some fairly serious > brokenness in memory handling in the hypervisor which was leading to > unnecessary swapping of the VMs. > > ESX 4.0 also has a new guest paravirtual SCSI driver which is supposed > to improve virtual disk performance by about 20% but I have yet to > test that. > > Tim > > _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
