Striping your Swap File in XP

All versions of Windows make use of a swap file. This is virtual memory and acts as hard drive storage space for memory items when you run low on actual physical memory. Use of the swap file slows down Windows quite a bit because hard drives are simply nowhere near as fast as system memory. But, you can speed up access to the swap file by using stripping. Stripping is a technique of RAID whereby data is spanned across more than one drive at the same time. Windows XP has code built-in which will stripe the swap file across two drives when you assign sizes to more than one partition. In order to take advantage of this, you need to have two or more hard drives in your system and place the swap file across the two separate drives, not simply two separate partitions on the same drive.

Go to Control Panel > System > Advanced > Performance / Settings. Hit the Advanced tab and go down to the virtual memory section and hit Change. Choose your first partition where you want the swap file, then select Custom Size and enter the size you want. If you set the initial size and max size to the same value, the swap will not be resized on the fly and can lead to better performance. Then choose another partition on a separate drive and do the same.

Windows will then split the swap file among the two drives.

Comments

  1. Larry Miller says:

    Actually putting the pagefile on a striped set will provide little benefit. A stripped set benefits most on large files that are read serially. The pagefile is large but it is not read serially but in relatively small blocks. Pagefile performance is governed primarily by seek time, not transfer time.

    Don’t waste a stripped set on the pagefile. Use it for large data files which will benefit most from it.

    Larry Miller
    Microsoft MCSA

  2. Robert Chaplin says:

    He did not say to put the page file on a stripped set. I think he said to create two separate swap files on two separate physical disks, and RAID-like page file features in Windows would give you performance benefits similar to a stripe set of disks.

  3. I’ve done research. There’s little to none factural information on this subject, and i think that even Microsoft knowledge base is giving misleading information on actual swap-paging system inner working. Read further to know why.

    In my search i’ve found a book by O’Reilly called “Windows 2000 Performance Guide”. In a chapter called “Memory management and Paging” detailing WindowsNT memory system inner workings there’s a info saying “Adding a second paging file spreads the paging I/O load across another physical disk and usually improves page fault resolution time substantially.”

    So this is all theory, how about practical proof? For this there’s system tool called Performance Monitor included in OS. Now, on a test system that uses page swapping quite heavily, that is Windows 2000, 64Mb RAM and two swap files on separate physical disks, according to Performance Monitor system usage of two swap files is symmetrical, usage percentage is similar. And subjectively system became more responsive.

    So i think there’s truth behind this article.

Leave a Reply