nt.ntfs.mft.txt

`Date: Tue, 27 Apr 1999 18:26:54 +0400  
From: Vladimir Dubrovin <[email protected]>  
To: [email protected]  
Subject: MFT problem  
  
Hello NTBUGTRAQ,  
  
Sorry for my bad English...  
  
Some times ago it was noticed the problem with MFT. I don't know if  
this problem was discussed in this list, so if it is - just discard  
this message.  
  
The problem is:  
  
Then creating a very large number of empty files on NTFS partition and  
then removing this files you loose a lot of space (up to 90% of  
volume!) and you couldn't recover this space without reformatting the  
NTFS volume. This problem occurs because NT allocates space in MFT  
(Master File Table, an internal NTFS database). Then the MFT reserved  
space ends NT allocates new space for MFT. The space allocated for MFT  
will never be released. (information "How NTFS Reserves Space for its  
Master File Table (MFT)" can be found in KB article Q174619).  
  
Then creating empty file (with zero length) it takes disk space  
olny in directory entry and MFT table. If you'll fill your NTFS volume  
with such files and then delete them the MFT table will take the most  
of your hard drive space (up to 90% as it was noticed before).  
  
You can reproduce this problem next way:  
  
It's better to use empty NTFS volume of small size - 50-100Mb - the  
results will be more distinctive.  
  
Check the free space on your NTFS volume.  
  
md temp  
for /L %i in (1,1,1000000) do type nul >temp/file.%i.tmp  
  
then you fill all the partition with this files - abort the circle.  
  
del /Q temp\*.*  
del /Q temp  
  
Now you can check free space on your hard drive. You've loosed it  
almost completely...  
  
By the way: it seems  
dir /A $MFT  
doesn't shows real MFT size, as it described in Microsoft  
documentation. At least you will never find the space you've loosed in  
any special file. But you can try some other utility, such as  
defragmentation utilities - usually they shows MFT reserved space...  
  
The problem is, that any user, who has "create" permition in any  
directory on NTFS volume can bring this volume down.  
It's specially interesting if your FTP server has "incoming"  
directory, or you offer free HTML pages for your customers on NTFS  
volume...  
  
This problem isn't solvable with some kind of disk quotas,  
because the files are empty...  
  
  
I've contacted Vitaly Savenkov from Russian department of Microsoft,  
[email protected].  
He forwarded me reply from developers:  
  
<><><><><><><>  
Dear ...,  
I'm sorry that I have to tell you the following.  
-  
My investigations and the answers from our Secondary Response Group  
confirmed, that the $MFT will never shrink.  
The only way is to reformat the Partition.  
This behavior is the drawback resulting from optimizing the  
NTFS performance. The main goal was to avoid fragmentation.  
-  
Possibly the best resolution for your situation is to use a  
single partition for the FTP Data. If the available space then  
goes under an acceptable level you can backup this partition  
and reformat it.  
  
I checked this with our Escallation Team and so i can say that  
this behavior of NTFS will not be changed.  
  
best regards,  
...  
<><><><><><><>  
  
So, now you can check it...  
  
  
+=-=-=-=-=-=-=-=-=+  
|Vladimir Dubrovin|  
| CSS Coordinator |  
| Sandy Info, ISP |  
=+=-=-=-=-=-=-=-=-=+=-=  
  
`