Used space on an "empty," formatted flash drive

Question

I recently purchased a SanDisk Cruzer CZ36 16GB USB 2.0 flash drive. The flash drive was formatted as FAT32 from the package. I will need to store files that are larger than 4GB on this flash drive, so I decided to reformat the flash drive as NTFS. (Also, the drive had some SanDisk SecureAccess software preloaded on it that I don't want.) On Windows 7, I right-clicked the drive and selected Format. I did a full format by unchecking the "Quick format" box.

After the format, however, Windows tells me that the drive is not completely empty. If I right-click on the drive and select Properties, Windows gives me this infomation:

Type:        Removable Disk
File system: NTFS

Used space:     96,169,984 bytes    91.7 MB
Free space: 15,912,419,328 bytes    14.8 GB

Capacity:   16,008,589,312 bytes    14.9 GB

Why is this the case, since I just formatted the drive? Is this to be expected? Or are some files still lingering on the drive?

When I open the drive on Windows Explorer, no folders or files appear, even when I tell Windows to show hidden folders and files. But, still, I find it worrisome that there is 91.7 MB some how being used on this "empty" drive.

Solution

This is normal. An "empty" NTFS filesystem has a number of internal files such as the master file table ("$MFT"), the log file used for filesystem recovery ("$LogFile"), the volume descriptor file ("$Volume"), and so on.

The largest one is probably the cluster allocation bitmap ("$Bitmap") that keeps track of what space is used and what space is free. This is pre-allocated when the filesystem is created.

Comments

[Paebbels]

In addition: This is not restricted to NTFS. Every file system stores itself on the same medium and requires some space. The size depends on the partition size and/or the file count.

[Andrew]

Thanks so much. So do you think 91.7 MB of used space is reasonable for a 16 GB flash drive?

[David Schwartz]

0.6% sounds reasonable to me.

[CivMeierFan]

Interesting. Do you have a source so I can delve further?

[David Schwartz]

@CivMeierFan You can start here or just punch something like "ntfs structure" into your favorite search engine.

[Jörg W Mittag]

@CivMeierFan: The best documentation about NTFS used to be the reverse-engineered specification on the Linux-NTFS Wiki. It was so comprehensive that – according to some curious webserver log entries – it seems it was actually used as training material inside Microsoft. Unfortunately, the Wiki, along with the entire Linux-NTFS project no longer exists. But you can still find some remnants at the Internet Archive's WayBack Machine.

[fixer1234]

This random computer-related fact doesn't really relate to the question.