I\u2019ve previously stated that you had to be careful with the Startup RAM setting in a cloud\/hosting scenario. The guest OS can only see the high-water mark of allocated RAM since the VM booted up. For example:<\/p>\n
- \n
- A VM is configured with 512 MB Startup RAM and 8 GB Maximum RAM<\/li>\n
- The VM boots up and the guest OS sees 512 MB RAM<\/li>\n
- The DMVSC integration component starts up<\/li>\n
- Pressure for RAM increases in the guest OS and maybe the VM increases to 768 MB<\/li>\n
- Pressure reduces and the VM is now using 612 MB<\/li>\n<\/ul>\n
Imagine a customer who owns this VM, logs into it, downloads the SQL installer and runs setup. Setup will fail because the installer requires 1 GB of RAM for SQL to run. The guest OS can only see 768 MB \u2013 the high water mark since the VM booted up. That\u2019s a helpdesk call. Now scale that out to hundreds or thousands of VMs. Imagine all the helpdesk calls. Sure; you\u2019ve saved some money on RAM, but you\u2019ve had to hire more people to close calls. Trust me \u2026 no wiki or knowledge base article will sort it out. I\u2019ve been on the hosting service provider side of the fence and I\u2019m a hosting customer too
![\"Smile\"](\"https:\/\/aidanfinn.com\/wp-content\/uploads\/2012\/10\/wlEmoticon-smile.png\")
<\/p>\nSo my advice for W2008 R2 was to set Startup RAM to be 1 GB of RAM. Sure, lots of VMs remain idle in a cloud \u2013 you\u2019d be amazed how many might never be logged into, even if there is a monthly invoice for them. You\u2019ve reduced the helldesk calls but you\u2019re still using up RAM.<\/p>\n
Enter Windows Server 2012 Hyper-V (and Hyper-V Server 2012) \u2026<\/p>\n
We have a new setting called Minimum RAM, allow a VM to balloon down to below<\/em> the Startup RAM when the VM is idle. All that idle RAM returns back to the host for reuse. How about this now:<\/p>\n
- \n
- The VM is configured with 1 GB RAM Startup RAM and 8 GM Maximum RAM<\/li>\n
- Minimum RAM is set to 256 MB<\/li>\n
- The VM powers up with 1 GB RAM, goes idle and balloons down to 320 MB RAM<\/li>\n
- After a week, the customer logs into the VM, attempts to install SQL Server. The RAM high-water mark is 1 GB and the SQL setup has no problems.<\/li>\n<\/ul>\n
No helldesk calls there! And it\u2019s done without the loss of performance associate with RAM over-commitment and second level paging.<\/p>\n
Technorati Tags: Virtualisation<\/a>,Hyper-V<\/a>,Cloud<\/a>,Windows Server 2008 R2<\/a>,Windows Server 2012<\/a><\/div>\n","protected":false},"excerpt":{"rendered":"I\u2019ve been doing some thinking about how to configure Dynamic Memory (DM) in a Windows Server 2012 Hyper-V cloud. One of the traits of a cloud is self-service. And that\u2019s why some thought is required. If you\u2019re not familiar with Dynamic Memory, then have a look at the paper I wrote on the feature as … Continue reading “Thinking About Cloud, Self-Service, and Hyper-V Dynamic Memory”<\/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":[172,181,195,117,118],"class_list":["post-13594","post","type-post","status-publish","format-standard","hentry","category-hyper-v","tag-cloud","tag-hyper-v","tag-virtualisation","tag-windows-server-2008-r2","tag-windows-server-2012"],"aioseo_notices":[],"jetpack_featured_media_url":"","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/13594","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=13594"}],"version-history":[{"count":0,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=\/wp\/v2\/posts\/13594\/revisions"}],"wp:attachment":[{"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13594"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13594"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aidanfinn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13594"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}