How do you change CLUSTER size in NTFS?


Big Moe

Can someone please tell me how to format my hard drive with NTFS and a 32K cluster size. I'm wanting to use NTFS but I don't like the default of a 4K cluster size that the XP installation CD uses.

I read somewhere that the command would be:
format C:/FS:NTFS /A:32

I created an MS-DOS startup disk and copied the to it. I booted up to the floppy and ran the command. It responded that the program cannot be run in MS-DOS mode.

Am I doing something wrong?


OSNN Veteran Addict
Last time that I checked a 32k cluster size would most likely not be worth it seeing as NTFS compression does not work above 4k cluster sizes. Also why would you want such a high cluster size? it would reduce your availible HD space since a cluster is indivisible and even if the file is not 32k it would take up a whole cluster and if the file was say 32.5k it would take up TWO clusters!

Also if you are trying to format a drive with data and an os already on it your gonna have to wipe it completely clean first. the you copied probably is not the default one that should be copied to a recovery disk is why it said can not be done in dos mode., you can boot from the XP cd and do it from there I believe.

Big Moe

Q, I'm just doing a little testing on my machine to see if there is a performance increase or not. I'm aware of all of the caveats that exist with a larger cluster size in NTFS. I had to perform a format of my hard drive anyway, I just wanted to "scratch that itch" of wondering if performance increases. I know I could see and feel the difference in cluster size with FAT32.

Curious, when you boot to the XP CD, how do you get to a command prompt or change the cluster size from there.

Big Moe

Unfortunately Partition Magic Pro 7 only allows me to change cluster sizes for FAT32 not the NTFS.


Big Moe,

You cannot run the version of FORMAT from NT/2000/XP within MS-DOS, the only way your going to format the drive is if you take it to another workstation with NT/2000/XP running, install the disk drive and format from the other workstation

By the way the command is:

format <drive_letter>: /fs:ntfs /a:32k

note the "k" at the end.



OSNN Veteran Addict
Originally posted by joansfella
Basically you cant change cluster size in ntfs and why would you want to anyway a larger cluster will just waste space on your H /d
Um you can easily change NTFS cluster size, you can't do it on a partition with data already on it but you can change it using the command line, and it doesn't necessarily waste harddrive space if you know what your doing.

The only time I've ever used a higher cluster size was on a separate drive that housed ONLY large video files...the bigger cluster size made access much faster and fragmentation non-existant, but it isn't good to have a higher then 4k cluster size on your whole drive if you have all sorts of different sized files on them

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