Relation hash table

I am trying to divide the buffer pool into 5 parts and i call these
clusters (different from postgres db clusters). What i want to do is to
make a mapping from the relations to these clusters. One relation belongs
to one cluster and a cluster can obviously have more than one relations. I
use a hash table to do this similar to the buf_table.c file. Right now i
don't know how many relations there are in total. I have just initialized
it to 100. The key is relation and the data is the cluster information.
Can anyone see any problems in using this approach.
Feed back will be greatly appreciated.

PS i am aware that because of OS caching this may not cause any
improvements.

thanks
nailah