{"id":10822,"date":"2010-08-26T18:55:19","date_gmt":"2010-08-26T18:55:19","guid":{"rendered":"https:\/\/aidanfinn.com\/?p=10822"},"modified":"2010-08-26T18:55:19","modified_gmt":"2010-08-26T18:55:19","slug":"hyper-v-host-freezes-when-dynamic-memory-vms-use-all-ram","status":"publish","type":"post","link":"https:\/\/aidanfinn.com\/?p=10822","title":{"rendered":"Hyper-V Host Freezes When Dynamic Memory VM\u2019s Use All RAM"},"content":{"rendered":"<p>This is a scenario I saw today when I configured a pair of virtual machines with Dynamic Memory and used up all available RAM.\u00a0 The Hyper-V parent partition locked up and became non responsive.\u00a0 The VM\u2019s were fine; they continued working away.<\/p>\n<p>The fault as I found, was mine, and mine alone.\u00a0 Virtual Machines with Dynamic Memory enabled could consume all memory on the host, leaving nothing for the parent partition.\u00a0 That\u2019s why we have a new registry key:<\/p>\n<ul>\n<li>HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersion Virtualization<\/li>\n<li>RED_DWORD value<\/li>\n<li>Name = MemoryReserve<\/li>\n<li>Setting = amount of MB to reserve for the parent partition, e.g. 2GB RAM (search my blog for details on memory for the parent partition).<\/li>\n<\/ul>\n<p>You must reboot the host after setting this registry value.\u00a0 I forgot to do this and the setting did not become effective.<\/p>\n<p>My host has 8GB RAM.\u00a0 Both VM\u2019s were configured with 512-4096MB RAM.\u00a0 The parent was using around 1.5GB.\u00a0 You can do the maths: 4096 + 4096 + 1536 &gt; 8192.\u00a0 Every byte of RAM appeared to be consumed when I pushed the VMs to their achievable maximum.\u00a0 The parent partition was locked up because it had no RAM to do anything.\u00a0 The only recourse was to do a hard reset.<\/p>\n<p>BTW, the tool I used to force the VMs to consume memory was consume.exe from the Windows SDK.\u00a0 It\u2019s a free download.<\/p>\n<p><em>EDIT #1<\/em><\/p>\n<p>Just to repeat: the problem was caused by my mistake.\u00a0 I should have rebooted after setting the registry value.\u00a0 And thanks to Serdar who has patiently answered a whole bunch of questions.<\/p>\n<div id=\"scid:0767317B-992E-4b12-91E0-4F059A8CECA8:89dac595-8242-4147-8be6-56c26b09f8f8\" class=\"wlWriterEditableSmartContent\" style=\"padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; display: inline; float: none; padding-top: 0px\">Technorati Tags: <a rel=\"tag\" href=\"http:\/\/technorati.com\/tags\/Virtualisation\">Virtualisation<\/a>,<a rel=\"tag\" href=\"http:\/\/technorati.com\/tags\/Hyper-V\">Hyper-V<\/a>,<a rel=\"tag\" href=\"http:\/\/technorati.com\/tags\/Windows+Server+2008+R2\">Windows Server 2008 R2<\/a><\/div>\n","protected":false},"excerpt":{"rendered":"<p>This is a scenario I saw today when I configured a pair of virtual machines with Dynamic Memory and used up all available RAM.\u00a0 The Hyper-V parent partition locked up and became non responsive.\u00a0 The VM\u2019s were fine; they continued working away. The fault as I found, was mine, and mine alone.\u00a0 Virtual Machines with &hellip; <a href=\"https:\/\/aidanfinn.com\/?p=10822\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Hyper-V Host Freezes When Dynamic Memory VM\u2019s Use All RAM&#8221;<\/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":[181,195,117],"class_list":["post-10822","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-hyper-v","tag-virtualisation","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\/10822","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=10822"}],"version-history":[{"count":0,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/10822\/revisions"}],"wp:attachment":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10822"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10822"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10822"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}