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tdknight avatar image
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SQL Server VSS Writer Number following GUID

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?

sql-server-general
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Cathyji-msft avatar image
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Cathyji-msft answered tdknight commented

Hi @tdknight,

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.


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Hi Cathyji-msft,

I understand the GUID in the physical_device_name column and the value in the device_type column indicate that it was a Virtual Device. But there is a number after the GUID that I am interested in.

The numbers in bold, after the closed curly bracket.

{C2C9435C-552F-4472-B5A0-847F8E8D9AF8}29
{AA45A63B-1675-4D20-B257-507911524428}29
{62822511-203B-4166-8BEB-24BCE4DD4F47}11

Tahnks.


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Hi @tdknight,

Thanks for your reply. As I mentioned above, I also search this from internet, but could not find any information explain the numbers.

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Sorry, I missed reading the last sentence.

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