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Change NTFS cluster size

Last response: in Windows XP
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February 22, 2010 3:14:52 PM

Hello,
Rather than NECRO an old thread let me list the tradeoffs and restate the question.

First, it appears the most common situation is a partition (typically the boot partition) that has been converted from FATxx to NTFS, where the resulting cluster size is 512K.

In general, a larger cluster size (such as 4096K) should result in fewer IO operations, meaning fewer waits for device completions, which should improve performance. OTOH, larger clusters waste more space, but if you have a large drive with plenty of free space, larger clusters should be better.

However, you can do other things to improve performance, such as moving your swap file to a different partition with larger clusters (since it's easier to back up and reformat a non-boot partition). Also, check your drive - it may perform a read-ahead, caching additional data, so if the drive is relatively unfragmented some of the benefit of larger clusters may disappear, and going through the exercise of reformatting may not be worth the effort.

Assuming one does want to proceed with changing the cluster size, what products can accomplish this? Partition Magic (Symantec) is apparently no longer available.
February 22, 2010 3:54:09 PM

Since most hard disks have fairly large on-board caches, I'd have to question the assumption that a larger cluster size will result in fewer IO operations. I'm happy to just go with the default cluster sizes.
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March 4, 2010 1:12:52 PM

Yes, I mentioned drive caches in my original post, and I'd be happy with the default cluster size of 4096K, too, but that's not what you got when you migrated from a Win9x OS (which mostly had 512K FAT clusters) to one of the NT descendants.

Consider the following: my wife's computer (a Dell 866 with XP Home upgraded from Win98) was agonizingly slow, and chronically sort on space in the boot partition. I converted to NTFS. I doubled memory. I added a second 32G drive (same make and model) and moved everything else off the original drive and expanded the boot partition to 32G.

All these steps helped, but not as much as you'd think. The last step was to completely eliminate the swap file settings for the C: drive so that the only swap settings were now on the second drive (note that this action has its own implications, primarily related to creating dumps, but I'll live with that).

The result was at least a 10x improvement in all areas: startup time (presentation of login dialog), user login (through completion of stuff like Norton initialization) and opening applications. For example, where Outlook previously took as long as 60 seconds to open and populate the inbox, it now opens in about 5 seconds.

Note that the swap file was previously split, and I know it was using space on both drives. It was eliminating the swap usage on C: that finally did the trick. The difference? C: was still stuck with the 512K cluster size from the original migration to XP, while the other partitions all had 4096K clusters (the default swap page size).

There are alot of boxes out there with 512K clusters on the boot partition (from migrations to Win 2K or XP) that could really benefit from a utility that can change the cluster size.

So ... does anyone know of a currently available utility (shareware or licensed) that can do this?
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March 4, 2010 1:30:49 PM
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March 4, 2010 4:10:05 PM

Thanks, iJack - that's what I need!
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March 4, 2010 4:10:21 PM

Best answer selected by djhill8262.
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October 26, 2011 3:18:28 AM

I dont see where I can set the size to 512 for the bytes per cluster in Partition Manager 11 Pro
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