Accidentally one the member has compressed the disk drives in the SQL Server. Before we go ahead an uncompress the disk drives, we need to make sure that the database is unaffected.

1. What is the normal database compression ratio when Hard Disk is compressed?
2. Do uncompression of the Hard Disk will affect the database integrity?
3. If teh disk drives are uncompressed, what is the expected space the database would take?

Thank you very much.


13 Years
Discussion Span
Last Post by karvinkoppa


I would get everyone out of the application / database before making a new backup of it. If you do not have an uncompressed backup of the database, then you could really be in trouble.

It is also possible that the volume is compressed, but the actual database file is not. Check the properties to be sure... because the filesystem (Microsoft Server) should automatically decompress the database when it is read... meaning it might be uncompressed! Go into Windows, and enable alternate colors for compressed files... the ones that are compressed will appear blue on your screen.

Check out http://www.ntfs.com/ntfs-compressed.htm

To answer your questions:

1) Depends on what is in your database. Raw numbers? Letters? Pictures? The data type has a direct relationship with how much can be compressed. I think a lot of people assume 50 percent.

2) It shouldn't, as the OS compressed the data, and you are not reporting any problems with it. I would still back it up to tape in a few places before doing something with it.

3) Assuming 50% compression ratio, when the file is expanded, it will be twice the size.


Thanks for your comments..

The database is running fine (with low performance) in compressed (disk drive) format. We need to make sure whether decompressing the disk drive will not harm the exisitng database.

Could please suggest/advice us how to recover the entire database which is in the compressed format to an uncompressed format without loosing any of the information?

Thanks once again.


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