Sizing Hyper-v Guests for cores use - best practices these days out of the total physical cores on a CPU?

i had question regarding hyper-v sizing guests , allocating cores..

in past think rule of thumb not put more vm's on given hyper-v server cores.. if had 8 cores, 8 vm's max.. , if vm required 4 cores, left 4, 5 max worst case..

in reading online sounds if thinking no longer applies?

case example of our new hyper-v server.. 

i have xeon e5-2650 v3 2.3 ghz 10 core.. 2 of them.. 20 physical cores, 40 hyper threaded..

i'm assuming ht doesnt count much.. said..

taking example of virtualizing exchange, think requires minimum of 4 cores.. assign 4 cores vm example... leaving 36 cores..

in past i'd assign more 1 core vm if needed it.. ie: instance new 2012 r2 file servers, still have set 1 single core , hammered dpm agents running sync tasks..

i thought read give vm's more cores might need , utilize needed..

so had 10 vm's using 4 cores.. using 40 of whats "available", old thinking no more vm's should added or assigned more cores, think depends on loading.. in our environment 20-30 concurrent hits time occur, 1 single core assigned, never see vm go above 15%..

so if have maxed out spread of cores, or maxed them out, still ok assign more vm's counts higher default of 1?

perhaps assign each vm 4 start no matter what, performance increases?

any on clarifying great, in advance

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tech, universe, everything: http://tech-stew.com plane crazy http://flight-stew.com

actually, have seen kinds of sizing guidelines.

the 1 has stood this:

a single vm should not have more vcpu total core count of physical server.

(a twist on yours true reasoning behind it)

so, if physical server has total of 8 cores.  no single vm should have more 8 vcpu (when runs on physical hyper-v server).

what trying accomplish preventing single vm impacting own vcpu processing threads (which spread across of physical cores).

i have seen 1 vcpu per physical core (at all, counting total number of vms) recommendation of specific application.  think either exchange or biztalk recommended long ago.  application specific , never intended applied vms.

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brian ehlert
http://itproctology.blogspot.com
learn. apply. repeat.

Windows Server  >  Hyper-V