It seems that you are only talking about ufs on solaris?

Let me add someother things:
on linux, use tune2fs -l /dev/sdxx

On hpux , solaris, and if using vxfs, you can use fstyp - /dev/your_device to check t he blocksize.
On these filesystem, the default block size is 8k.

And on AIX, the default blocksize is 4K.