{"id":7552,"date":"2025-08-13T20:34:58","date_gmt":"2025-08-13T19:34:58","guid":{"rendered":"https:\/\/tomaskalabis.com\/wordpress\/?p=7552"},"modified":"2026-02-13T11:50:21","modified_gmt":"2026-02-13T10:50:21","slug":"proxmox-windows-vm-slow-disk-write-fix","status":"publish","type":"post","link":"https:\/\/tomaskalabis.com\/wordpress\/proxmox-windows-vm-slow-disk-write-fix\/","title":{"rendered":"Proxmox \u2013 Fixing Slow Disk Read\/Write Speeds in Windows Guest VM"},"content":{"rendered":"\n<h3>Proxmox \u2013 Fixing Slow Disk Read\/Write Speeds in Windows Guest VM<\/h3>\n<p data-start=\"601\" data-end=\"761\">If you\u2019ve ever deployed a Windows Server guest on <strong data-start=\"651\" data-end=\"665\">Proxmox VE<\/strong> and noticed painfully slow disk performance \u2014 especially <strong data-start=\"723\" data-end=\"739\">write speeds<\/strong> \u2014 you\u2019re not alone.<\/p>\n<p data-start=\"763\" data-end=\"1144\">In my case, I was running the latest <strong data-start=\"800\" data-end=\"813\">Proxmox 9<\/strong> with a <strong data-start=\"821\" data-end=\"844\">Windows Server 2025<\/strong> Guest VM hosted on a <strong data-start=\"860\" data-end=\"893\">Dell SC3020 storage array<\/strong>, connected over <strong data-start=\"910\" data-end=\"937\">Fibre Channel\u00a0<\/strong>of course the multi-path configured.\u00a0<br data-start=\"938\" data-end=\"941\" \/>Despite having the latest <strong data-start=\"967\" data-end=\"985\">VirtIO drivers<\/strong> installed and using a <strong data-start=\"1008\" data-end=\"1034\">VirtIO SCSI controller<\/strong>, write performance was extremely poor \u2014 to the point where even simple file copies were frustratingly slow.<\/p>\n<p data-start=\"763\" data-end=\"1144\"><a href=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.01.07.png\"><img decoding=\"async\" loading=\"lazy\" class=\"size-large wp-image-7553 aligncenter\" src=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.01.07-494x326.png\" alt=\"\" width=\"494\" height=\"326\" srcset=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.01.07-494x326.png 494w, https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.01.07-288x190.png 288w, https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.01.07-768x507.png 768w, https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.01.07.png 966w\" sizes=\"(max-width: 494px) 100vw, 494px\" \/><\/a><\/p>\n<p data-start=\"1146\" data-end=\"1340\">After much testing, the real breakthrough came from enabling <strong data-start=\"1207\" data-end=\"1227\">Write Back cache<\/strong> on the virtual disk. This simple setting improved write speeds dramatically and completely resolved the issue.<\/p>\n<p data-start=\"1146\" data-end=\"1340\"><a href=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.33.46.png\"><img decoding=\"async\" loading=\"lazy\" class=\"size-large wp-image-7556 aligncenter\" src=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.33.46-494x312.png\" alt=\"\" width=\"494\" height=\"312\" srcset=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.33.46-494x312.png 494w, https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.33.46-288x182.png 288w, https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.33.46-768x485.png 768w, https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/Screenshot-2025-08-13-at-21.33.46.png 1054w\" sizes=\"(max-width: 494px) 100vw, 494px\" \/><\/a><\/p>\n<p data-start=\"1146\" data-end=\"1340\">\u00a0<\/p>\n<p data-start=\"1146\" data-end=\"1340\">\u00a0<\/p>\n<p>\u00a0<\/p>\n<p>\u00a0<\/p>\n<p>\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Proxmox \u2013 Fixing Slow Disk Read\/Write Speeds in Windows Guest VM If you\u2019ve ever deployed a Windows Server guest on Proxmox VE and noticed painfully slow disk performance \u2014 especially &#8230;<\/p>\n","protected":false},"author":2,"featured_media":7557,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[1],"tags":[425],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Proxmox \u2013 Fixing Slow Disk Read\/Write Speeds in Windows Guest VM - tomaskalabis.com<\/title>\n<meta name=\"description\" content=\"Trouble with slow disk writes in Windows Server VM on Proxmox? 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Learn how enabling Write Back cache on VirtIO SCSI disks can boost performance.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/tomaskalabis.com\/wordpress\/proxmox-windows-vm-slow-disk-write-fix\/\" \/>\n<meta property=\"og:site_name\" content=\"tomaskalabis.com\" \/>\n<meta property=\"article:published_time\" content=\"2025-08-13T19:34:58+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-02-13T10:50:21+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/proxmox_logo.png\" \/>\n\t<meta property=\"og:image:width\" content=\"230\" \/>\n\t<meta property=\"og:image:height\" content=\"219\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Tomas Kalabis\" \/>\n<meta name=\"twitter:label1\" content=\"Napsal(a)\" \/>\n\t<meta name=\"twitter:data1\" content=\"Tomas Kalabis\" \/>\n\t<meta name=\"twitter:label2\" content=\"Odhadovan\u00e1 doba \u010dten\u00ed\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minuta\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/tomaskalabis.com\/wordpress\/proxmox-windows-vm-slow-disk-write-fix\/\",\"url\":\"https:\/\/tomaskalabis.com\/wordpress\/proxmox-windows-vm-slow-disk-write-fix\/\",\"name\":\"Proxmox \u2013 Fixing Slow Disk Read\/Write Speeds in Windows Guest VM - tomaskalabis.com\",\"isPartOf\":{\"@id\":\"https:\/\/tomaskalabis.com\/wordpress\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/tomaskalabis.com\/wordpress\/proxmox-windows-vm-slow-disk-write-fix\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/tomaskalabis.com\/wordpress\/proxmox-windows-vm-slow-disk-write-fix\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/tomaskalabis.com\/wordpress\/wp-content\/uploads\/2025\/08\/proxmox_logo.png\",\"datePublished\":\"2025-08-13T19:34:58+00:00\",\"dateModified\":\"2026-02-13T10:50:21+00:00\",\"author\":{\"@id\":\"https:\/\/tomaskalabis.com\/wordpress\/#\/schema\/person\/8e7e83f618a561ed3734a38cef4cf1d6\"},\"description\":\"Trouble with slow disk writes in Windows Server VM on Proxmox? 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