Problems with CAS OS Server

hello,
I have the next structure:

2 redundant WinCC servers for S5 PLCs
2 redundant WinCC servers for S7 PLCs
1 CAS WinCC server for tag and alarm loggin
28 WinCC clients

The WinCC version is v6.0 SP3

My configuration for TagLogging fast and slow and Alarm Logging is:
Time period of all segments: 1 Month / 20 GB
Time period covered by a single segment: 8 Hour / 500MB

When the system has 2 weeks running the CAS WinCC goes too slow and I have to delete some backup's files und begin again. I have tested the same structure but only with a client and runs correctly. Is there any limitation with the amount of clients?

Also I have a client with theCONNECTIVITY PACKSiemens software for read data from WinCC database and show tags in excel format. When the connectivity pack attempt to accede to the server, this also runs too slow und I have to delete some backup's files.

I am not sure if I update WinCC software these problems will be resolve.

thanks,
David