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Moving and resizing partitions

Sometimes you may have a need to change the layout of the partitions on your hard drive. The list of the "officially supported" operations for this is fairly limited in Windows.

"Officially supported" partition management operations in Windows are:

  • Create partition
  • Delete Partition
  • Expand an existing NTFS partition to occupy some free space. This is only supported on Windows NT/2000/XP, and you can't do this on your system and/or boot volumes.

There are some variations of these, involving primary and extended partitions and logical drives, but the general idea is still the same.

As the filesystem conversion goes, only the "filesystem upgrade" options are provided, namely

  • Convert FAT16 to FAT32 in Windows 98/ME
  • Convert FAT16/FAT32 to NTFS in Windows NT/2000/XP

For any other operation like moving or resizing partition or splitting one partition in two, the official way is to backup data, delete existing partitions, create new partition, restore data from a backup.

Third party tools (the most widely known is Partition Magic) provide a way to perform a complete list of operations on all the filesystem flavors available. Their feature lists are fairly impressive, including moving, resizing, merging, and splitting partitions, filesystem "downgrades" (e.g. NTFS to FAT16) and so on. The most striking thing is that all these operations can be done while data is on the partition.

This creates an irresistible temptation to go ahead moving filesystems all around without having a proper backup. Many people got caught in this pitfall, many terabytes of data wasted. Many more will follow.

The partition resizing or conversion is a very complicated process. For example, resizing a FAT partition involves renumbering of all file locations. This requires to read and rewrite every entry in every directory on the volume. This also requires some considerably long time (in general, all sophisticated operations on the filesystems are time-consuming).

During conversion operation the filesystem remains in severely inconsistent state for long periods of time. Severely inconsistent means that ScanDisk or CHKDSK tools aren't going to help you if the conversion process gets interrupted for one reason or another. During conversion, it is like two nonfunctional sets of the filesystem structures coexist on the partition: one for the old filesystem which is already under demolition, the other for the new filesystem which is yet inoperative. This dramatically increases the complexity of the task for data recovery tools (like ZAR). Algorithm convergence issues will occur because in most cases program cannot reliably separate two filesystem data sets. The program may end up oscillating between two possible solutions, or just pick arbitrary one, or even worse it may pick an arbitrary mix of two.

When FAT-to-NTFS (or vice versa) conversions are involved, there is a trick for us to use. We perform two separate recovery runs, one chasing FAT filesystem, the other for NTFS filesystem. Then we merge the results, filter bad files and duplicates and finally the result is (in most cases, eh) satisfactory. This trick does not work when the conversion involves similar filesystems, like FAT16-to-FAT32 conversion, or when the partition is just resized or moved.

Here comes the conclusion:

There are great tools which give us the ability to move/resize/convert our partitions quickly and without hassle. This is ultimately good. But there are some things you need to do to ensure their smooth and successful operation.

  • Be sure to check your drives for corruption with common tools (ScanDisk/CHKDSK) before starting the process. This is a good thing to do regularly anyway.
  • Ensure no external interruptions of the process. Have the backup power source available (at least to survive a power spike). Keep people away from the computer while the process is underway, so they did not reboot it by mistake.
  • Do not attempt filesystem conversion/resize/move operations on a computer that has known stability issues.
  • If the program appears hang, avoid restarting the computer without giving it a good wait. We've once seen Partition Magic progressing through the partition for about two hours without a single visible change.
  • Ultimately, create a backup of the important data on the filesystem before the conversion.
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