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MS-Windows Troubleshooting

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Disk Thrashing

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Symptom:

There is a lot of disk activity, even when performing mundane activities that wouldn’t normally be expected to access the disk.

Possible Causes and Remedies:

• It is possible that the machine does not have enough physical memory and is therefore spending much of its time swapping. This is likely to be the case if disk activity seems to be related to performing any activities on the workstation and there is no disk activity when the machine is idle.
  • The obvious (and quite possibly the only) solution is to add more memory. In my experience NT has a tendency to thrash if there is less than 96MB installed. See also: Recommendations on how much memory you should put in your PC/laptop.
  • It is possible that Windows NT is keeping more in memory than it should. Check in the registry under ‘HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Control\ Session Manager\ Memory Management’ that:

    DisablePagingExecutive	=0	This enables paging of kernel pools.
    LargeSystemCache	=0	Uses a ‘small’ file cache.

• It may be an application or service that is running on the workstation.
• Although unlikely, on a machine that has a generous amount of physical memory it is possible that Windows NT is being over-zealous in trying to free up memory.

  • To force Windows NT to swap less out of memory try setting the following in the registry under ‘HKEY_LOCAL_MACHINE\ SYSTEM\ \CurrentControlSet\ Control\ Session Manager\ Memory Management’:

    DisablePagingExecutive	=1	This disables paging of kernel pools.
    LargeSystemCache	=1	Uses a ‘large’ file cache.

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These notes have been tested with Windows NT4.