MIRROR DATABASE WITH DIFFERENT TASK SIZE BY NODE?(FOR EXPENSIVE AND SLOW SYSTEM)

Hi, we have mirrored databases, now we have three nodes. Primary, backup, async. They are sync by journals and with some TB each node (expensive storage).

I would like to have a scenario where the two nodes (Primary and backup) have the same amount of messages (purge task of x days) , both as failover, but the asynchronous node should have more messaging, as much as the storage allows us. We want to use this node so provider can give support(search old messages), but not have databases in production that are so large that they are hardly consulted.

Any ideas?

Thanks in advance!