Does Windows Server File Compression slow Oracle DB performance?

Question

I'm starting a new a new contract and I get to troubleshoot their Oracle instance... I'm more apps and sql, but I'll be trying to figure out their crashes and slow performance. Go figure.

I can guess at reasons for some slowness... they want me to review their queries and tune where I can... DB and queries... Time for me to brush off those old Oracle DBA books.

I don't get access to Oracle for a bit, but I've got access to the Win 2008 R2 server and MS SQL Server. I notice that their MS SQL backups are in pretty poor shape, with 987+ backups across 6 or so databases... they were down to 42M of space left on their 173G drive.

Looking at the system over all, I see that they are keeping their DB and databases on compressed drives. I would think that this would give them a performance hit, but I really don't know.

Would this affect the performance of their Oracle and MS SQL negatively?

Update: As I look around their system, I see other patterns of Worst Practices: Multiple applications on one server: Oracle DB, OracleBI, MS SQL 2008, Oracle WebLogic, Sharepoint... All are on a single spindle -- 1 TB set in 5 virtual drives. Almost all applications are in directories with folder/file compression set. The sizing for the drives is currently a bit tight. The Oracle "drive" has 4% free space (4.3 G free). The MSSQL drive had what... 0.02% free before I deleted some old backups...

I will recommend additional drives (which probably won't happen) or to at least re-size the "Drives" and share out some of the 400 GB remaining on C:

The 4.3 GB free on the Oracle drive may not be a critical piece, but I can't tell until I can get Oracle up and running long enough to see what their DBs and conditions are. So, "performance"-wise, it's a ZERO... at least MSSQL is running.

Thanks for your input... now off to find and digest the Oracle logs.