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CHKDSK: "RAW filesystem" message
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Sometimes a damaged volume may look like it lost its filesystem type. Various
error messages may appear, most common being The volume X: is not formatted. Do you want to format it
now?
The disk in drive X: is not formatted.
There was an error accessing drive X:. The disk is not
formatted.
Also a CHKDSK tool will complain that is is unable to perform a RAW filesystem
recovery.
The type of the filesystem is RAW.
CHKDSK is not available for RAW drives. |
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To know how to deal with it, we need to discuss the basics first. The filesystem type is recorded at least in two separate places
- In the partition table (MBR, sometimes referred to as a
legacy-style partition) or in the LDM database (when
dynamic disks are used).
- In the volume boot sector.
Three significantly different combinations are thus possible.
- Both partition table and volume boot sector provide consistent
information about the filesystem type. This is how the things are supposed
to be when the volume is online and operational.
- Only one of these places contains proper information, or the information
is contradictory (e.g. partition table lists the volume as NTFS, while the
boot sector indicates it is the FAT32).
- Neither partition table nor volume boot sector contain filesystem type
information (the partition table will in this case indicate the special
filesystem type of zero, i.e. unused volume). This can happen during normal
operation and is pretty legal configuration state. It appears when you
create a volume (e.g. using Disk Management applet) but do not format it at
the same time. You can even assign a drive letter to this unformatted
volume, as illustrated below (notice the underlined "H:" drive which has no
filesystem type defined).
If the volume filesystem type information is unavailable, attempting CHKDSK
against the volume will result in the following message:
The type of the filesystem is RAW.
CHKDSK is not available for RAW drives.
Sometimes, the volume fails in such a way that it becomes RAW. In most cases
the failure will be associated with a sudden reboot (per power failure or the
STOP error). Several causes are possible: partition table, LDM database, or the
volume boot sector corruption, or (on the NTFS volume) when certain records in
both MFT and MFT mirror are damaged beyond easy recognition.
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The data recovery should not be complicated because the volume
location info is still available. Be advised that some arbitrary filesystem type
may be associated with the volume when you attempt to identify it amongst the
list of the available volumes.
Notice the highlighted volume - it is the same H: volume
featured in the earlier screenshot. It has the correct size (128MB) and the
correct on-disk location (starting at 200+40+40 = 280MB from the start of disk),
but the filesystem type of "Large FAT16" is not a good bet because the
volume is in fact NTFS - the filesystem type information in the LDM database got
corrupt (yeah, I know because I did it in purpose). This fact will be later
discovered by ZAR and the appropriate decision will be made to treat the volume
as NTFS, and in this test case an exact recovery is ultimately achieved.
In a real world case, the recovery expectations vary depending on the damage profile and locality.
Overall, I'd expect a good yield. Exact recovery is possible if the damage is
confined to the boot sector(s) and/or partition table (however there is no easy
way to tell if it is). Suggested course of action is thus as usual: to download
our data recovery tool (click here for a download page) and
try it. Be sure to check this page as well.
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End of story, idiom: When all your files have been restored. -- ZAR Unabridged Dictionary
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