Ntbackup Causes Cache to Grow During Restore

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

When you run a restore of a big file with the Windows NT Backup tool you may see that the performance of the user interface and applications suffers. This happens in both the Restore and the Verify phase. You will see the problem with files bigger than physical memory.

When you take a look at this in Performance Monitor, you will find that the cache is very large (from 50 percent to 90 percent of physical memory) and the process working sets have shrunk.

MORE INFORMATION

The CreateFile API has a flag, FILE_FLAG_SEQUENTIAL_SCAN, that is especially useful when copying files. It tells Cache Manager not to try to increase the file cache when requests for this handle arrive. Hence, Memory Manager does not have to shrink the applications working set to accommodate the bigger cache.

Although Windows NT Backup uses this flag during Backup, it does not do so in the Restore phase.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

Keywords : kbbug4.00 kbfix4.00 ntbackup NTSrvWkst
Version : WinNT:4.0
Platform : winnt
Issue type : kbbug