Celerra NX4 rebuilding and cache

Hi. I have an issue with a Celerra NX4. I hope  this is the right place to ask this question.

The NX4 still works fine, but once in a while we have to replace a disk drive. The rebuilding process takes many hours and the perfomance is severey impacted.

First of all , the rebuilding and equalizing process can take as long as 30 hours or more. Some times 30 hours rebuilding and the 20 more equalizing. Is this normal ?

Anyway while this process is in progress the cache is disabled, that is what affects the perfomance of the NFS server more. Is there a way to enable it ?

The product is :

• Celerra NX4
• CLARiiON AX4-5F8
• Software Version: 6.0.61-0

Thank you very much