[Linux-NTFS-Dev] Re: FAT, NTFS, CIFS and DOS attributes

Szakacsits Szabolcs szaka at sienet.hu
Thu Jan 6 14:19:59 GMT 2005

On Wed, 5 Jan 2005, Steven French wrote:

> For sparse files, I don't mind it being a "read only" attribute (ie you 
> can not set the sparse bit, it is silently ignored).   

People who use ntfsclone to efficiently backup NTFS fully to remote cifs
servers would like it a lot.

Example: currently creating a mountable image of a 180 GB NTFS where 20 GB
is used ends up 180 GB allocated space on remote NTFS via cifsfs or smbfs
because they don't support FSCTL_SET_SPARSE. If FSCTL_SET_COMPRESSION were
supported too (this means these commands should be just sent to the remote
cifs servers) then the allocated space would be only about 10 GB. 

The current situation wastes too much space thus people either use a
remote Unix (unfortunately often they don't have yet because many are in
the testing Linux, migration phase) or drop the mountability feature.

> There are files which are compressed in NTFS on servers and it would be 
> useful for the client application or VFS to know this so it could be 
> decompressed before being read but I don't know an easy way to do this at 
> this point and it needs more investigation.

Hmmm, this is transparent. I don't think you should worry much about this
in cifsfs, except the interface to user land how to forward the "get" and
"set" of these attributes to the underlaying filesystems.


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