From time to time, I\u2019ll be asked to power down virtual machines in our production environment. I also run a test virtual machine on the cluster to test things like Live Migration after doing upgrade work. Normally, I\u2019d like to keep it powered down, just to save 512MB of RAM and the occasional CPU cycle. But it seems to me, that Microsoft does not like us to keep powered down virtual machines on the cluster.<\/p>\n
My first clue was in VMM. VMM tries to protect the cluster reserve in a Hyper-V cluster. In other words, VMM will change the status of a cluster object to a warning if you overcommit the resources. For example, if you have 58GB of RAM for VM\u2019s across your N+1 3 node cluster, then it\u2019ll complain when you deploy 58GB+ of VM RAM. One would assume that VMM would only calculate the running VM\u2019s. However, I can confirm that it does include the RAM assignments to powered down VM\u2019s as well. I can understand this conservative approach \u2026 it\u2019s the sort of thing a banker would do if they didn\u2019t want to bankrupt their bank\u2019s loan book ;-) You have to allow for a scenario where the VM will be powered up. Who\u2019s to say that there isn\u2019t a tester or developer at the other end of a Self-Service Portal, consuming their quota points, and eager to power up the VM\u2019s at any moment.<\/p>\n
The next clue is in OpsMgr. I\u2019ve imported the Microsoft Windows Cluster management pack. A highly available virtual machine is a resource from clustering\u2019s point of view. Surely you deployed it on a cluster (as a highly available virtual machine) for a reason? Shouldn\u2019t it be running? That\u2019s how the management pack sees it. An object is created in OpsMgr for every monitored cluster resources, i.e. virtual machine, and its status will go to critical if the resource is stopped, i.e. the virtual machine is powered down. You\u2019ll get an alert and notifications will go out. If you are running SLA reporting then you\u2019ll get a nice red mark all over your SLA. Whoops!<\/p>\n
So what should you do with those powered down VM\u2019s? If it is going to be down for a long time then you should move it to the VMM library. There you have cheaper storage, and hopefully lots of it. Importantly, the VMM cluster reserve will be OK. OpsMgr will stop complaining after a little while about a failed cluster resource.<\/p>\n
What if this power down is a short term thing? You should obviously add resources to the cluster to resolve the VMM cluster reserve warning because you won\u2019t have an N+1 (or greater) cluster with enough resources to handle a failed host (or hosts). You can use the Health Explorer in OpsMgr to put the critical resource (the powered down VM) in the cluster into maintenance mode, thus eliminating alerts. You should do that before powering down the VM.<\/p>\n
Long term, if lots of VM\u2019s will be powered down and up, you might want to create a dedicated, lower priority, cluster for this. You can customize the monitoring not to care about cluster resources being up or down. You can probably safely ignore warnings about VMM cluster reserve being exceeded too.<\/p>\n
From time to time, I\u2019ll be asked to power down virtual machines in our production environment. I also run a test virtual machine on the cluster to test things like Live Migration after doing upgrade work. Normally, I\u2019d like to keep it powered down, just to save 512MB of RAM and the occasional CPU cycle. … Continue reading “Powered Down Virtual Machines on a Hyper-V Cluster”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[20],"tags":[181,83,195,196,117],"class_list":["post-10677","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-hyper-v","tag-operations-manager","tag-virtualisation","tag-vmm","tag-windows-server-2008-r2"],"aioseo_notices":[],"jetpack_featured_media_url":"","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/10677","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10677"}],"version-history":[{"count":0,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/10677\/revisions"}],"wp:attachment":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10677"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10677"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10677"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}