\u201cWhat\u2019s the rule of thumb on the number of VMs you should put in a CSV?\u201d\u00a0 That\u2019s a question I am asked on a regular basis.\u00a0 We need to dig into this.<\/p>\n
When you have a cluster of virtualisation hosts using shared storage systems, you need some sort of orchestration to say which host should access what folders and files.\u00a0 That\u2019s particularly important during Live Migration and failover.\u00a0 Without orchestration you\u2019d have chaos, locks, failed VMs, and corruption.<\/p>\n
One virtualisation cluster file system out there does it\u2019s orchestration in the file system itself.\u00a0 That, in theory<\/em>, places limits on how that file system can scale out.<\/p>\n Microsoft took a different option.\u00a0 Instead, each cluster shared volume (CSV) has an orchestrator known as a CSV Coordinator that is automatically created and made fault tolerant.\u00a0 The CSV coordinator is a highly available function that runs on one of the clustered hosts.\u00a0 By not relying on the file system, Microsoft believes they have a more scalable and better performing option.<\/p>\n How scalable?\u00a0 A few years ago, EMC (I believe it was EMC, the owner of VMware, but my memory could be failing me) stood on a stage at a Microsoft conference and proclaimed that they couldn\u2019t find a limit on the scalability of CSV versus performance on their storage platform.\u00a0 In other words, you could have a monstrous CSV and place lots and lots of 64 TB VHDX files on there (GPT volumes grow up to 16 EB).<\/p>\n OK; back to the question at hand: how many VMs should I place on a CSV.\u00a0 I have to give you the consultant\u2019s answer: that depends.\u00a0 The fact is that there is no right answer.\u00a0 This isn\u2019t VMware where there are prescribed limits and you should create lots of lots of \u201clittle\u201d VMFS volumes.<\/p>\n First, I\u2019d say you should read my paper on CSV and backup<\/a>.\u00a0 Now keep in mind that the paper was written for Windows Server 2008 R2.\u00a0 Windows Server 2012 doesn\u2019t do redirected I\/O (mode) when backing up VMs from CSV.\u00a0 In that document I talk about a process I put together for CSV design and VM placement.<\/p>\n Next, have a look at Fast Track, Microsoft\u2019s cloud architecture.\u00a0 In there they have a CSV design where OS, page file, sequential files, and non-sequential files are split into VHDs on different CSVs.\u00a0 To me, this complicates things greatly.\u00a0 I prefer simplicity.\u00a0 Plus I can\u2019t imagine the complexity of the deployment automation for this design.<\/p>\n An alternative is to look at a rule of thumb that many are using: they have 1 CSV for every host in their cluster (or active site in a multi-site cluster).\u00a0 Beware here: you don\u2019t want to run out of SCSI-3 reservations (every SAN has an unadvertised <\/em>limit) because you\u2019ve added too many CSVs on your SAN (read the above paper to learn more).<\/p>\n My advice: keep it simple.\u00a0 Don\u2019t overthink things.\u00a0 Remember, Hyper-V is not VMware and VMware is not Hyper-V.\u00a0 They both might be enterprise virtualisation platforms but e do things differently on both platforms because they both work differently.<\/p>\n \u201cWhat\u2019s the rule of thumb on the number of VMs you should put in a CSV?\u201d\u00a0 That\u2019s a question I am asked on a regular basis.\u00a0 We need to dig into this. When you have a cluster of virtualisation hosts using shared storage systems, you need some sort of orchestration to say which host should … Continue reading “What\u2019s The Maximum Number Of Hyper-V VMs You Can Put In Cluster Shared Volume?”<\/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":[63,181,99,195],"class_list":["post-12537","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-failover-clustering","tag-hyper-v","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\/12537","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=12537"}],"version-history":[{"count":0,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/12537\/revisions"}],"wp:attachment":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12537"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12537"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12537"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}