If a large number of files are to be stored, a two-tier structure can be used at the root of the symbol store. The first 2 letters of the filename are used as an intermediate folder name.
To use a two-tier structure, place a file called index2.txt in the root of D:\SymStore\Symbols. The content of the file is of no importance. When this file exists, symsrv.dll will create and consume files from the two-tier tree using this structure:
From https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/symbol-store-folder-tree
To use a two-tier structure, place a file called index2.txt in the root of D:\SymStore\Symbols. The content of the file is of no importance. When this file exists, symsrv.dll will create and consume files from the two-tier tree using this structure:
From https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/symbol-store-folder-tree