Knowledge Base

Incorrect report on disk free space under DFS

Article ID: 177127

Article Last Modified on 8/23/2007

Microsoft Windows NT Workstation 4.0 Developer Edition
Microsoft Windows NT Server 4.0 Standard Edition
Microsoft Windows 95
Microsoft Windows 2000 Advanced Server
Microsoft Windows 2000 Professional Edition
Microsoft Windows 2000 Server
Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
Microsoft Windows Server 2003, Standard Edition (32-bit x86)
Microsoft Windows XP Professional
Microsoft Windows XP Home Edition
Windows Vista Business
Windows Vista Enterprise
Windows Vista Home Premium
Windows Vista Ultimate

This article was previously published under Q177127

SYMPTOMS

The Disk Free Space reported in Windows Explorer or in a Command Prompt on a Distributed File System (DFS) client for a DFS share is always the Disk Free Space of the drive containing (hosting) the DFS root.

CAUSE

This problem occurs because of a limitation in the server message block (SMB) protocol. The only SMB packet that is available to obtain the free disk space of a volume is TRANS2_QUERY_FS_INFORMATION with a sub-command of SMB_QUERY_FS_SIZE_INFO. Unfortunately, this command uses the Tree ID from the tree connect to determine which volume to query. If you access a mount point through a share on another volume, the tree connect happens to the share. Therefore, the Tree ID refers to the volume that the share is on, not on the volume that the mount points to. This limitation is scheduled to be fixed in the SMB 2.0 protocol.

MORE INFORMATION

The free disk space information that you see in Windows Explorer or ithat you see by running a command-line command on a domain based Distributed File System (DFS) is incorrect. You see disk information about the drive that hosts the SYSVOL share of the Domain Controller you are connected to. Additionally, "Free space" and "Used Space" information may be displayed incorrectly in Windows Explorer. This problem occurs if you have mapped a drive to a share that links to a mounted volume by using NTFS volume mount points or by using symbolic links.

Microsoft has confirmed this to be a problem in Windows NT version 4.0. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

REFERENCES

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

205524 How to create and manipulate NTFS junction points

Additional query words: "free space", "used Space", mountpoint, symbolic link, junction point, reparse point, MountedVolume, properties, 839570, WindowsSE.84857, network drive, mount point volume, JUNCTION, bytes free, DFS, domain-based DFS, capacity

Keywords: kbbug KB177127