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.
Answer
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.
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