Comment by da_chicken

I am thinking about that. I don't think most data is read that often in an OLTP system.

I think a very small amount of data is read very often. However, until your DB gets very large, that data is going to end up as data pages cached in memory. So that data is extremely cheap to read.

I also think a significant amount of data that is generated in an OLTP system is written and never read, but you still had to pay the cost to write it. If you have an audit log, chances are you never need to look at it for any one piece of data. But you definitely had to write all the metadata for it.

But I'm also assuming that writes are at least 10 times as expensive as reads. More so if what you're modifying has indexes, since indexes are often functionally identical to a partial copy of the entire table. Indeed, I think that 10 times mark is conservative. Most RDBMSs use transaction logging and some kind of locking on writes. There's data validation and integrity checks on inserts and updates (and deletes if you have foreign keys).

I think 1 write to 10 reads is still write-heavy.