In addition to these factors, collocation happens to be another key source of noise. By collocation I mean VMs doing the same/similar work running on the same hypervisor. This happens under low capacity situations when the scheduler could not enforce anti-affinity.
Subbu > On Apr 22, 2015, at 5:09 AM, George Shuklin <george.shuk...@gmail.com> wrote: > > Yes, it really depends on the used backing technique. We using SSDs and raw > images, so IO is not an issue. > > But memory is more important: if you lack IO capability you left with slow > guests. If you lack memory you left with dead guests (hello, OOM killer). > > BTW: Swap is needed not to swapin/swapout, but to relief memory pressure. > With properly configured memory swin/swout should be less than 2-3. > > On 04/22/2015 09:49 AM, Tim Bell wrote: >> I'd also keep an eye on local I/O... we've found this to be the resource >> which can cause the worst noisy neighbours. Swapping makes this worse. >> >> Tim >> >>> -----Original Message----- >>> From: George Shuklin [mailto:george.shuk...@gmail.com] >>> Sent: 21 April 2015 23:55 >>> To: openstack-operators@lists.openstack.org >>> Subject: Re: [Openstack-operators] over commit ratios >>> >>> It's very depend on production type. >>> >>> If you can control guests and predict their memory consumption, use it as >>> base >>> for ratio. >>> If you can't (typical for public clouds) - use 1 or smaller with >>> reserved_host_memory_mb in nova.conf. >>> >>> And one more: some swap sapce is really necessary. Add at least twice of >>> reserved_host_memory_mb - it really improves performance and prevents >>> strange OOMs in the situation of very large host with very small dom0 >>> footprint. >>> >>> On 04/21/2015 10:59 PM, Caius Howcroft wrote: >>>> Just a general question: what kind of over commit ratios do people >>>> normally run in production with? >>>> >>>> We currently run 2 for cpu and 1 for memory (with some held back for >>>> OS/ceph) >>>> >>>> i.e.: >>>> default['bcpc']['nova']['ram_allocation_ratio'] = 1.0 >>>> default['bcpc']['nova']['reserved_host_memory_mb'] = 1024 # often >>>> larger default['bcpc']['nova']['cpu_allocation_ratio'] = 2.0 >>>> >>>> Caius >>>> >>> >>> _______________________________________________ >>> OpenStack-operators mailing list >>> OpenStack-operators@lists.openstack.org >>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators > > > _______________________________________________ > OpenStack-operators mailing list > OpenStack-operators@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators _______________________________________________ OpenStack-operators mailing list OpenStack-operators@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
