After presenting on the topic of Hyper-V to over 250 people (including some VMM) over the last 3 weeks, I\u2019ve become aware that the term \u201cSnapshot\u201d confuses people.\u00a0 There is an unfortunate amount of confusion created by many different but similar solutions\/features:<\/p>\n
Hyper-V Snapshot<\/span><\/strong><\/p>\n This is the ability (just like in VMware) to capture a virtual machine\u2019s state (memory, CPU, system state, and disk contents) in a point in time.\u00a0 You can do some work, and then revert back to that snapshot, thus returning the VM to where it was back then, undoing all the changes made since the snapshot.\u00a0 You can have lots of snapshots, all tiered, and branched.<\/p>\n Hyper-V snapshots are<\/em>\u00a0 supported in production.\u00a0 But they are not supported by many of the applications you\u2019d install in a VM, e.g. SQL Server, Exchange, etc.\u00a0 I\u2019m not a fan of snapshots in production, in fact, I hate them because of the problems that people create for themselves (long story where people assume<\/span> all sorts of silly things that are convenient for them at the time).\u00a0 But I do use Hyper-V snapshots in lab environments to reset tests or demos.<\/p>\n Checkpoint<\/span><\/strong><\/p>\n This is what System Center Virtual Machine Manager (SCVMM) calls a snapshot.\u00a0 Yup, it\u2019s confusing.<\/p>\n EDIT: Microsoft listened to feedback and renamed the Hyper-V snapshot to checkpoint in WS2012 R2. Now it matches SCVMM and shouldn’t be confused with other kinds of snapshot.<\/p>\n Volume Shadow Copy Service (VSS) Snapshot<\/span><\/strong><\/p>\n This kind of snapshot is an NTFS volume snapshot that allows Windows to backup hot files that are being used (e.g. virtual machines) or databases with data\/log consistency (e.g. SQL Server or Exchange).<\/p>\n In the Hyper-V world, you can backup VMs (even running ones) using Hyper-V VSS compatible backup products such as DPM 2010 or Altaro.\u00a0 VSS creates a snapshot of the NTFS volume that contains the running VMs\u2019 files and then backup can hit the snapshot.<\/p>\n This snapshot is a VSS snapshot, not a Hyper-V Snapshot.\u00a0 You won\u2019t see it in Hyper-V Manager or in SCVMM.\u00a0 It exists purely as a hot file backup mechanism.<\/p>\n Interestingly, whereas Hyper-V snapshots may not be supported by many applications, this kind of backup can be, e.g. SQL Server and Exchange.\u00a0 However, some services, such as Domain Controllers, do not support restoring this kind of backup (in AD it causes USN rollback).<\/p>\n When I\u2019m asked for advice, I tell people to use this kind of backup to \u201csnapshot\u201d a VM instead of Hyper-V snapshots.\u00a0 There isn\u2019t the pain\/mess of mismanaging VHDs, AVHDs and merges, and it is supported by almost every app you\u2019ll need in a VM.<\/p>\n SAN LUN Snapshot<\/span><\/strong><\/p>\n In a SAN, you can create a snapshot of a LUN.\u00a0 This duplicates the LUN.\u00a0 How the duplication works depends on the SAN.<\/p>\n The VSS Snapshot mechanism can leverage this to speed up backup by using a SAN manufacturer provided Hardware VSS provider.\u00a0 Instead of doing a software based VSS snapshot, it will create a SAN snapshot of the relevant LUN and that can then be used by the VSS enabled backup product.\u00a0 It\u2019s especially useful for Hyper-V clusters with CSV where you want to minimise the amount of Redirected I\/O (Mode or Access).<\/p>\n This week I heard that some are telling customer to use a manually created SAN LUN snapshot as a form of backup\/restore on an hourly basis.\u00a0 Painful and it\u2019s probably consuming expensive disk \u2013 they\u2019d be better off using an efficient backup solution that writes to more economic disk.<\/p>\n Fixing the Confusion<\/span><\/strong><\/p>\n As you can imagine, all this overuse of the term \u201csnapshot\u201d doesn\u2019t help.\u00a0 It\u2019s one thing for hardware VS Microsoft, but it\u2019s another this when Hyper-V, SCVMM, and Windows VSS cause the confusion.\u00a0 If I had one suggestion then it would be this:<\/p>\n Change the term \u201cSnapshot\u201d in Hyper-V to \u201cCheckpoint\u201d.\u00a0 VSS isn\u2019t going to change, and you\u2019re not going to get the SAN vendors to change.\u00a0 Doing this would also increase consistency in Windows Server 8.<\/p>\n After presenting on the topic of Hyper-V to over 250 people (including some VMM) over the last 3 weeks, I\u2019ve become aware that the term \u201cSnapshot\u201d confuses people.\u00a0 There is an unfortunate amount of confusion created by many different but similar solutions\/features: Hyper-V Snapshot This is the ability (just like in VMware) to capture a … Continue reading “Confusion Over Hyper-V and \u201cSnapshots\u201d”<\/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":[55,181,193,195],"class_list":["post-11935","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-backup","tag-hyper-v","tag-system-center","tag-virtualisation"],"aioseo_notices":[],"jetpack_featured_media_url":"","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/11935","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=11935"}],"version-history":[{"count":0,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/11935\/revisions"}],"wp:attachment":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11935"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11935"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11935"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}