HA is when we make a virtual machine highly available by placing it on a cluster of hosts, e.g. a group of Hyper-V hosts in a Windows Server Failover Cluster, or a group of ESXi hosts in a vSphere cluster.\u00a0 If a host has a failure VM can be failed over to a different host.\u00a0 This means that an automated system provides better levels of availability than you get with non-clustered hosts.\u00a0 Typically, the failed host has crashed or powered down, and the VM is booted up on a different host.<\/p>\n
Live Migration (aka VMotion)<\/span><\/strong><\/p>\n Live Migration is a system where a running virtual machine can be moved from host A to host B with zero downtime.\u00a0 It is different from HA because it is more proactive than a failover operation.\u00a0 For example, Live Migration will be used by an administrator to move a VM from one host, that is going to have some maintenance operation, to another host with spare capacity.<\/p>\n Windows Server 2012<\/span><\/p>\n I have brought up this topic because in Hyper-V, Live Migration and HA went hand in hand, because they both required a Hyper-V cluster.\u00a0 That\u2019s changing.<\/p>\n In Windows Server 2012 the tie between Live Migration and Failover Clustering has been broken.\u00a0 All you will need to do Live Migration is a 1 Gbps network, meaning you can live migrate a VM between two non-clustered hosts, between clusters, and of course, between clustered hosts.<\/p>\n As you now know, Live Migration is not high availability.\u00a0 I\u2019m sure the tech media is going to confuse things \u2013 in fact, I believe they already are Don\u2019t get me wrong; Live Migration without clustering is an excellent addition.\u00a0 Many choose not to do HA because they cost of downtime is less than the cost of HA for some applications.\u00a0 They will like the agility and mobility they\u2019ll now get with zero downtime.<\/p>\n With the coming changes in Windows Server 2012 (WS2012), I thought I\u2019d take a few minutes to explain the difference between HA and Live Migration. High Availability (HA) HA is when we make a virtual machine highly available by placing it on a cluster of hosts, e.g. a group of Hyper-V hosts in a Windows … Continue reading “High Availability (HA) and Live Migration”<\/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":[63,181,195,109],"class_list":["post-11814","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-failover-clustering","tag-hyper-v","tag-virtualisation","tag-windows-8"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t![\"Smile\"](\"https:\/\/aidanfinn.com\/wp-content\/uploads\/2011\/09\/wlEmoticon-smile8.png\")
If you want your virtualised workloads to be independent of hardware\/host fault then you must still install a Hyper-V cluster \u2026 and don\u2019t forget that Windows guests need appropriate clustering (you can move a MSFT license from one hardware to another once every 90 days so you really should license hosts).\u00a0 If you work in a small\/medium business, then don\u2019t fret \u2013 Windows Server 2012 doesn\u2019t require that expensive SAN any more \u2013 have a look at my previous posts on Storage Pools where you can now store HA VMs on active\/active clustered file shares using cheaper JBOD.<\/p>\n