I haven't done anything in Solaris since the time they switched from steam-powered machines to electrical ones, but i have suffered with ASM and DBAs requesting it a lot. Maybe this will be helpful to you:

There is virtually no such thing as a performance hit if the system is not extremely low on memory and/or you do some real-time processing of high loads. Under "normal" conditions there is enough memory left over for file cache so that the difference between a filesystem and a raw device is negligible. Everything else is just myths told from one DBA to the other. Anyway, give them whatever they want, it isn't worth the time to argue with DBA about technics - if they would understand it, they would be SysAdmins like us, wouldn't they?

With ASM you end with "anonymous" disks and nobody really is helped by such crap. About 10 years ago i had a system where several DB instances where running in parallel, al with ASM. The system had ~250 hdisk devices. Guess what? The DBAs finally managed to tell us the wrong hdisk number (something like "hdisk145" instead of "hdisk154") to delete and one DB came to a screeching halt. But since i had no method to find out what a certain disk is used for or if it is used at all (for the OS they all look unused) this is what had to happen sooner or later.

The compromise i set up was to create volume groups from the disks, create logical volumes in them and only give these out to the DB as raw device. Now, this was AIX and the Solaris wording is different, but as far as i know "zpool" is a sort-of LVM itself so you surely know how to translate that to proper Solaris procedures. Never give them disk devices as raw devices! Just give them volumes without a filesystem on it. Always make sure you have some control layer (via the LVM) to take care of things.

I hope this helps.

bakunin