{"id":14478,"date":"2013-04-12T07:38:57","date_gmt":"2013-04-12T06:38:57","guid":{"rendered":"https:\/\/aidanfinn.com\/?p=14478"},"modified":"2013-04-12T07:38:57","modified_gmt":"2013-04-12T06:38:57","slug":"passthrough-disks-are-still-supported-by-ws2012-hyper-v-live-migration-but-with-limits","status":"publish","type":"post","link":"https:\/\/aidanfinn.com\/?p=14478","title":{"rendered":"Passthrough Disks \u2013ARE\u2013 Still Supported By WS2012 Hyper-V Live Migration, But With Limits"},"content":{"rendered":"<p>I recently <a href=\"https:\/\/aidanfinn.com\/?p=14435\" target=\"_blank\">reported<\/a> on a new KB article that says:<\/p>\n<blockquote>\n<p>Changes and improvements in Windows Hyper-V Server 2012 no longer support pass-through disks if Live Migration is to be used.<\/p>\n<\/blockquote>\n<p>In other words, Live Migration was <strong><em><u>allegedly<\/u><\/em><\/strong> not supporting the use of passthrough disks.<\/p>\n<p>That article was <strong><em><u>incorrect<\/u><\/em><\/strong>.&#160; <\/p>\n<p>The story is:<\/p>\n<p>1) Hans Vredevoort told me that found a contradicting blog comment\/response by Jeff Woolsey where he stated that Live Migration of VMs with passthrough disks would be supported in what I\u2019ll call legacy scenarios:<\/p>\n<blockquote>\n<p><em>Pass through disks are still supported with Windows Server 2012 Hyper-V Live Migration (just like they were with Windows <\/em><i><em>Server 2008 R2 Hyper-V) as long as the migration of a clustered VM and the pass through disk is managed by the cluster. For migrations outside of a cluster, such as:<\/em><\/i><\/p>\n<ul>\n<li><em>Shared Nothing Live Migration or<\/em><\/li>\n<li><em>Using standalone hosts with file on a SMB share (without clustering enabled)<\/em><\/li>\n<\/ul>\n<p><em>\u2026pass through disks aren\u2019t supported because the pass through disk doesn\u2019t have a way to move between hosts. <\/em><\/p>\n<\/blockquote>\n<p>That makes total sense.&#160; The passthrough disk (which is not a CSV) has to be passed from one host to another, and only a cluster-managed disk can do this.<\/p>\n<p>Therefore the new scenarios in WS2012 Hyper-V <em>cannot<\/em> support Live Migration.&#160; Again, that makes total sense:<\/p>\n<ul>\n<li>Non-clustered SMB-stored-VM Live Migration \u2013 you can\u2019t store a LUN on a file share!<\/li>\n<li>Shared-Nothing Live Migration \u2013 until you can transport a LUN from one server to another Star-Trek-style, it isn\u2019t happening.<\/li>\n<\/ul>\n<p>2) Who was correct, Jeff Woolsey or the KB article?&#160; We needed clarity so I reached out to the Hyper-V group in Redmond.&#160; They responded overnight and Jeff was right.&#160; The KB article was \u2026 a \u2026 bit enthusiastic (I personally loved the message \u2013 I\u2019m quite clear in my training that I\u2019ll smack anyone who I find using passthrough disks).&#160; In fact, that KB article has been deleted by Microsoft.<\/p>\n<p>So those of you who are panicking about your passthrough disks, you can calm down now.<\/p>\n<p>\u2026<\/p>\n<p>However \u2026<\/p>\n<p>The advice from <em>everyone <\/em>who knows anything about Hyper-V is that you should switch to using VHDX files.&#160; This isn\u2019t just me.&#160; Check out any of the Virtual Machine MVPs on this topic.&#160; Read what <a href=\"http:\/\/workinghardinit.wordpress.com\/\" target=\"_blank\">Didier Van Hoye<\/a> or <a href=\"http:\/\/hyper-v.nu\" target=\"_blank\">Hans Vredevoort<\/a> (both being the top 2 storage guys in our group IMO) have to say on the topic.<\/p>\n<ul>\n<li>VHDX scales out to 64 TB<\/li>\n<li>It has new health features to limit corruption<\/li>\n<li>It supports 4K sector matching for performance<\/li>\n<li>It offers the legacy VHD types, where Fixed will be nearly the same speed as the underlying disk<\/li>\n<\/ul>\n<p>I heard loads of complaints over the \u201cdeath\u201d of passthrough disks in the last 7 days.&#160; To you I say, you need to put down your toys of the 2000s. and join us in the 2010s.&#160; We virtualise now for flexibility.&#160; The business demands it, and passthrough disks are not flexible.<\/p>\n<p>The one argument I\u2019ll give some credence to is \u201cI can\u2019t hot expand a VHDX\u201d.&#160; If you are hot expanding LUNs every couple of days then you\u2019ve got other issues, but I too would like this feature.<\/p>\n<p>Anywho, panic over.&#160; You can Live Migrate a VM with passthrough disks as long as both the VM and the passthrough disks are managed by a Hyper-V cluster.&#160; I\u2019m going back to my lazy vacation day now.<\/p>\n<div id=\"scid:0767317B-992E-4b12-91E0-4F059A8CECA8:1c7bb198-ebe4-4902-b45e-953aee6fc02f\" class=\"wlWriterEditableSmartContent\" style=\"float: none; padding-bottom: 0px; padding-top: 0px; padding-left: 0px; margin: 0px; display: inline; padding-right: 0px\">Technorati Tags: <a href=\"http:\/\/technorati.com\/tags\/Hyper-V\" rel=\"tag\">Hyper-V<\/a>,<a href=\"http:\/\/technorati.com\/tags\/Virtualisation\" rel=\"tag\">Virtualisation<\/a>,<a href=\"http:\/\/technorati.com\/tags\/Storage\" rel=\"tag\">Storage<\/a>,<a href=\"http:\/\/technorati.com\/tags\/Live+Migration\" rel=\"tag\">Live Migration<\/a><\/div>\n","protected":false},"excerpt":{"rendered":"<p>I recently reported on a new KB article that says: Changes and improvements in Windows Hyper-V Server 2012 no longer support pass-through disks if Live Migration is to be used. In other words, Live Migration was allegedly not supporting the use of passthrough disks. That article was incorrect.&#160; The story is: 1) Hans Vredevoort told &hellip; <a href=\"https:\/\/aidanfinn.com\/?p=14478\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Passthrough Disks \u2013ARE\u2013 Still Supported By WS2012 Hyper-V Live Migration, But With Limits&#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":[181,74,99,195],"class_list":["post-14478","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-hyper-v","tag-live-migration","tag-storage","tag-virtualisation"],"aioseo_notices":[],"jetpack_featured_media_url":"","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/14478","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=14478"}],"version-history":[{"count":0,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/14478\/revisions"}],"wp:attachment":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14478"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14478"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14478"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}