Is it possible to remove capacity from Data Domain?

HI,

Can anyone tell me if it is possible to remove capacity form a Data Domain?

We have a DD890 with both ES20 and ES30 enclosures and a DD990 with ES30 enclosures. We want to move the ES30 shelves from the 890 and add them to the 990.

Assuming there will be enough capacity left afterwards can the filesystem be reduced and the shelves removed from the DD890?

Thanks

DJ