You might have heard that WS2012 R2 Hyper-V changed how it performs backups of virtual machines but not heard how.\u00a0 I\u2019ll give you a glimpse of what that change was in this post.<\/p>\n
First some terminology:<\/p>\n
In the past, VSS<\/a> is used to create a VSS snapshot of the volume(s) containing the files of a VM that is to be backed up.\u00a0 The snapshot was mounted and the required files (identified by the Hyper-V Writer) were backed up.\u00a0 The process was pretty complex and could lead to problems for some customers.\u00a0 The quality of storage hardware VSS writers had too much impact on the process.\u00a0 Once you have a pretty clean environment (network\/storage design, patching, drivers and firmware), backup was the one problem that could hurt.\u00a0 CSV 2.0 sorted out most of that, but Microsoft wanted to simplify the backup process.<\/p>\n Thanks to live merging of checkpoints (snapshots) that was added in WS2012, and the experience Microsoft has gained by using checkpoints (snapshots) for other features (such as Hyper-V Replica), WS2012 R2 Hyper-V has switched to using checkpoints instead of VSS snapshots.<\/p>\n Now a checkpoint is created of every virtual machine that is to be backed up.\u00a0 Writes are temporarily redirected to the checkpoint\u2019s AVHDX\/AHVD file(s).\u00a0 This gives the backup requestor a clean & crash consistent copy of the virtual machine\u2019s VHD or VHDX files that are safe to read.\u00a0\u00a0\u00a0 After the backup, the checkpoint is merged and the job is done.<\/p>\n Note: You might notice that a VSS snapshot is still taken of the relevant volume(s).<\/em><\/p>\n We\u2019ve moved from application consistent backup to the next (small) step down with a crash consistent backup.\u00a0 This isn\u2019t a big deal \u2013 not for backup experts anyway.\u00a0 For products like SQL Server or Exchange, restoring this VM is like someone reset the VM.\u00a0 The restored database starts up, does a quick cleanup, and carries on operating as it did before the backup operation.\u00a0 In return, we get a much simpler backup process that should prove to be more resilient and selective.<\/p>\n","protected":false},"excerpt":{"rendered":" You might have heard that WS2012 R2 Hyper-V changed how it performs backups of virtual machines but not heard how.\u00a0 I\u2019ll give you a glimpse of what that change was in this post. First some terminology: Volume Shadow Copy Service (VSS) Snapshot: VSS performs a snapshot of a volume to get a consistent backup of … Continue reading “How WS2012 R2 Hyper-V Backup Works”<\/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,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"_wpcom_ai_launchpad_first_post":false,"footnotes":""},"categories":[20],"tags":[55,195,120],"class_list":["post-15759","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-backup","tag-virtualisation","tag-windows-server-2012-r2"],"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