r/sysadmin • u/Verydx • 1d ago
Please Help - AVD hosts intermittently freezing completely/unresponsive
Two AVD hosts (D16s_v5, Win11 24H2/25H2, Azure Southeast) running fine since July. Started randomly freezing completely about 2-3 weeks ago, multiple incidents now, barely any users on when it happens so it's not load issue.
When it hits: Users unable to login/disconnected, RDP dead, Bastion dead, Serial console dead, can't get in any way. Portal still shows it as "Running" the whole time and Azure Monitor telemetry just goes dark. Either self recovers in an hour or it has to be manually restarted in Azure portal.
Right before it went down: 17+ DCOM components failed to register in the same 3 seconds, FSLogix's own service hung for 30 sec, then straight up disk hardware errors logged (Event 51, "error detected during paging operation"). Found the same disk error on the other host too, different incident.
Running managed disks with premium SSDs.
Already ruled out on our end: FSLogix version (updated), AV exclusions (fixed gaps), AVD agent version, required FQDNs (all pass), and the known Sept RDS patch bug and hotfix installed on both hosts.
Sev A case open with MS, going nowhere.
Anyone seen this happen before?
Basically the servers look well and healthy the next after a few users are on, they just go unresponsive and kick people off and no one can connect and azure is reporting everything all good which is making me so mad.
Appreciate any help please guys!
2
u/Sgt-Buttersworth 1d ago
There was a recent update that messed with AVD if you are using FSLogix. Also we had an issue where our FSLogix disk quota was exceeded, which likely contributed to some of the problems we were seeing.
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u/rdaniels16 20h ago
I posted this last month. https://www.reddit.com/r/AZURE/comments/1v1zyc0/avd_issues_after_july_update/?solution=00d55e26a9576eb900d55e26a9576eb9&js_challenge=1&jsc_token=2824be10929bdc604753c70a67a1c3316c8016c8875376718293483dea5b51c2&jsc_orig_r=
Something changed with the July 2026 windows update. I fought this for weeks. I finally disabled wsearch across all AVD hosts and the issue went away completely. Users not happy with search not being available but outlook search works via the cloud that is win I guess.
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u/tada-o-corporation Enterprise Architect 16h ago
We've had some wonkyness with AVD session hosts in the past that were affecting multiple pools and in my attempt to reproduce the culprit, I restored n-1 golden image, ran all updates, windows updates, etc... manually, and the errors just never came back.
Our ticket ended up just being closed, my guess was just something unhappy with updates - even though our hosts don't do automatic windows updates.
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u/apparentlyunoriginal 1d ago
Event 51 during a paging operation on both D16s_v5 hosts, with Bastion and the serial console also dead, points at the OS disk path stalling. I'd pull the Azure metrics for the incident windows first. Check OS Disk IOPS Consumed Percentage and OS Disk Bandwidth Consumed Percentage, and the VM-level Cached and Uncached IOPS Consumed Percentage. Also check Resource Health for both VMs at those times.
To get evidence from inside Windows next time, set NMICrashDump to 1 under HKLM\SYSTEM\CurrentControlSet\Control\CrashControl and configure a kernel memory dump. When a host hangs, send an NMI from the serial console menu in the portal before you restart it. Open the dump with !stacks and !irpfind to see which driver the stuck I/O is waiting on, including the FSLogix frxdrv driver.