Currently when Confluence is running in a clustered mode the only storage option for attachments is database.

While it might be a convenient solution to get a cluster up a running quickly, putting extra strain on the db can quickly result into performance problems as many Confluence admins have seen in the past.

An ideal solution would be to add support for NAS/SAN filesystems which would be shared by all the cluster nodes.

I understand that it might not be easy for some to set up an appropriate filesystem, but on the other hand, when someone wants to run a confluence cluster he/she usually has the skills and resources available for setting up a shared filesystem.