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Joachim_Otahal's avatar
Joachim_Otahal
Iron Contributor
Feb 02, 2024

Server vNext 26040 and Server 2022 deduplication data corruption

Following scenario gives me, easy to reproduce on various newer comptuer with SSD-based storage, data corruption with deduplication. Server 2019 does not have that issue. Reproduced on several Intel and AMD machines with 16 or more (real, non SMT) cores. Can be reproduced with HDD storage on i7-4960x CPU too, but with less that 50% probability.

Host: Server 2019, Server 2022 or Windows 11.

1-st level VM: Server 2022 or Server vNext 25xxx or 26xxx, nested-v active for that VM. Have a drive 😧 for your nested VMs.

2-nd level Guests: More than one, since at least two running concurrently are needed to trigger the issue. OS does not matter, but easiest are Window VMs running Windows Update.

As long as deduplication for 1-st level VM is not activated everything is fine. But if you activate deduplication for drive D:, where the nested VMs reside, you will get data corruption, in some cases even so bad that the dedup-chunkstore shows up as filesystem defect.

 

Ready-to-reproduce packages: Those are created on a Server 2019 host, so Server 2019 and ANY later OS should be able to import them. No network connection needed, not even a Hyper-V switch. Needs a computer with 32 GB RAM and 'round 100 GB of free space on a non-system drive.

Unpack to non-system-drive, import into Hyper-V, start the VM. Then follow the text file on the desktop.

Result as video, here Server 2022: https://www.joumxyzptlk.de/tmp/microsoft/S2022-Nested_Deduplication_VDI-Hyperv_profile_kills_filesystem_v2.mp4

Package with Server vNext 26040: https://www.joumxyzptlk.de/tmp/microsoft/Server-vNext-26040-nested-dedup-problem-export-from-S2019-host.7z

Package with Server 2022: https://www.joumxyzptlk.de/tmp/microsoft/S2022-nested-2023-09-30-exported-from-S2019-host.7z

Package with Server 2019, just as "See, Server 2019 works fine!" counter proof: https://www.joumxyzptlk.de/tmp/microsoft/S2019-nested-2023-10-07-exported-from-S2019-host.7z

 

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