What’s the between a Quick format and a regular format during a “clean” installation of Windows?

March 7th, 2007

Question: When installing a new copy of Windows or reformatting a non-system drive with NTFS, you get the option of Quick or Full format. I understand that a full format does the entire drive, but a quick just does the header. However, for a drive that has never been formatted before, does a quick format really slow down write operations later on when using areas of the disk that have never been used before? And if I have an NTFS drive, and perform a quick format on it, is the effect the same, or does the fact that it has been used previously negate the problem?

To answer this question, we first need to understand what the difference between a quick format and a full format is.  To do this we turn to the Microsoft Knowledgebase:

When you choose to run a regular format on a volume, files are removed from the volume that you are formatting and the hard disk is scanned for bad sectors. The scan for bad sectors is responsible for the majority of the time that it takes to format a volume.

If you choose the Quick format option, format removes files from the partition, but does not scan the disk for bad sectors. Only use this option if your hard disk has been previously formatted and you are sure that your hard disk is not damaged.

If you installed Windows XP on a partition that was formatted by using the Quick format option, you can also check your disk by using the chkdsk /r command after the installation of Windows XP is completed.

So the main difference between quick and full is that full checks and re-applies the file structure to the whole disk as opposed to just wiping the file allocation table and directory table.  Because the file allocation table and directory table is wiped by a quick format, and the rest of the drive is ready to accept files, there's no performance overhead in writing files to the disk.

It is not possible to quick format a brand new unformatted drive because  the file structure has to be laid out ready to receive files.  So that answers the part about performance relating to a disk that's not been used before.

Hope that helps!

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