SQL Server VSS Writer Number following GUID

TD Knight 1 Reputation point
2021-03-19T18:14:12.77+00:00

I have seen the GUID in the physical_device_name of the backupmediafamily table in SQL Server because of the VSS Writer. What is the number following the GUID? For example, the 28, 29, and 11: {DB7707D5-32D5-4C1A-831C-BF85E274DFAA}29 {9302BBEE-563D-40EB-8FBA-EC1935C2250C}29 {B3CD77DB-8C51-4206-B509-CEC4A571D529}29 {4C76A7E5-DD9F-49C8-B0BD-2D8EBF07E4C5}29 {C2C9435C-552F-4472-B5A0-847F8E8D9AF8}29 {AA45A63B-1675-4D20-B257-507911524428}29 {62822511-203B-4166-8BEB-24BCE4DD4F47}11 {9BB3E977-8738-41B9-901B-86BEEF7AC27D}28 What are they? I've been told they are "the type of backup". Is there a reference document that explains them all?

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  1. CathyJi-MSFT 20,656 Reputation points Microsoft Employee
    2021-03-22T07:35:44.12+00:00

    Hi @TD Knight ,

    SQL Server supports virtualization-aware backup solutions that use volume shadow copy (VSS) also named volume snapshots. For example, SQL Server supports Hyper-V and VMware backup.

    You should notice that these backups have value 7 in the column "device_type" (7 means Virtual device). These rows are actually very useful, for example it help to know that the Virtual Machine backups are running full database backups on a SQL Server instance. there's no trace of these backup files since they are above the scope of the virtual machine (above the level of your machine) - these are triggered by the host (Hyper-V or VMware for example).

    Quote from the blog SQL Server: physical_device_name in the Backup log shows GUID to get more.

    But i did not find any blog explain the numbers.


    If the response is helpful, please click "Accept Answer" and upvote it, thank you.