The compression itself is not the issue, however - Windows will load compressed drivers just fine. As a result, when the CBS Scavenger compresses these files, the actual cdrom.sys file in system32\drivers The problem is that it also compresses some driver files (such as cdrom.sys), and those driver files may be hardlinked to the live copy in system32\drivers folder. (presumably, this change was introduced in 8.1 due to complaints related to low available disk space on low-end Windows tablet devices, where disk space is tight).Īfter you install or remove an update, the CBS Scavenging scheduled task will re-check the WinSXS folder and compress some of the files. The updated servicing stack in Windows Server 2012 R2 / Windows 8.1 compresses some rarely used files in c:\windows\WinSxS as a part of CBS (Component Based Servicing) Scavenging process.
This looks like a known bug related to 4KB-sector ('Advanced Format') disk drives and NTFS compression.
