Performance problems HP & Online DS

Hello, We have two Online DS engines (7.23.uc1) which are running in a replica situation. These engines are running on a HP-D series machine. We have performance problems which results in checkpoints above the 5 seconds. This means : -We are putting a lot of data on the machine or -The Engine has a performance problem. The amount of data which we are putting on the system is about 750 Kb at these 5 minutes. Then the engine need 5 seconds to write this data to disk --> 150 Kb/s. Has onyone who has the engine running on a HP D-series also these problems, or can anyone tell me how to solve this problem (Informix can't to solve the problem) Greetings, Bart Huls