General :: Data On Disk Drive Management By OS - Getting Base I/O Unit Size?

I want to ensure I have done all I can to configure a system's disks for serious database use. The three areas I know of (any others?) to be concerned about are: I/O size: The database engine and disk's native size should either match, or the database's native I/O size should be a multiple of the disk's native I/O size. DMA: Disks that are capable of Direct Memory Access (eg. IDE) should be configured for it.
Write-caching: When a disk says it has written data persistently, it must be so! No keeping it in cache and lying about it.

I have been looking for information on how to ensure these are so for CentOS and Ubuntu, but can't seem to find anything at all. I want to be able to check these things and change them if needed. The actual hardware involved is very modest. The point is to get the most out of what hardware we do have, even though it's "not very serious hardware" from a broader perspective.