A bit of pedanticism:
> So we would like to know how you recommend copying PostgreSQL database files in Windows OS to perform file system level backups.
(For Example – The recommended way in Linux is to use tar format.)
That is not what a file-system-level back up is, and not what tar does at all. Tar basically creates a file that contains other files, and would be subject to the same issues a copy would be.
A file-system level backup is just that, a backup done by the file system itself, usually via an atomic snapshot. LVM, ZFS, and BTFS are all capable of doing this in Linux and *BSD. The filesystem will store the current state of the filesystem somewhere in an atomic manner, i.e. nothing else happens when the snapshot is made.
I think NTFS can do volume shadow copies, but I havn't used windows in perhaps a decade and have never done so as an admin or professionally.
Jim