Uploaders windows support

[Lyndon-Li]

fs uploader and block uploader support Windows nodes:

• For fs uploader, skip the Windows system folders in volume's root
• For block uploader, choose linux node only since Windows doesn't support block mode volumes yet

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 59.18%. Comparing base (03d0bd9) to head (cb22dfc).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controller/data_upload_controller.go	0.00%	2 Missing and 1 partial ⚠️
pkg/uploader/kopia/snapshot.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8569   +/-   ##
=======================================
  Coverage   59.17%   59.18%           
=======================================
  Files         370      370           
  Lines       39568    39591   +23     
=======================================
+ Hits        23416    23433   +17     
- Misses      14673    14677    +4     
- Partials     1479     1481    +2     

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[ywk253100]

Shouldn't we only check the volume mode when we cannot determine the OS via the annotation just like checking the file system type if scFsType == "ntfs"?

[Lyndon-Li]

At present, Windows nodes doesn't support blockMode volumes. Or in another word, pods running in Windows nodes won't be with blockMode volumes.

Therefore, until Kubernetes supports it in a future release and Velero also supports blockMode on Windows nodes, we should always use linux nodes for blockMode volumes.

[ywk253100]

What will happen when Kubernetes supports the Window block mode volumes in future? Although the PVC is attached to a Windows node, the "Linux" is returned as the OS, and the backup pod will run on the Linux node to handle the Windows block mode volumes, is this the expected behavior?

[Lyndon-Li]

blockMode volumes are technically be backupable from either linux node or Windows node.
Running blockMode volumes backups on Windows nodes require further efforts.

Therefore, once Windows block mode volumes are supported, on the one hand, we can run all the backups on linux nodes with no efforts; one the other hand, as the ultimate solution, we will support Windows blockMode volumes backup.