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Moving and resizing partitions
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
- 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
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.