What is the client writing to the disk?

[mestar]

My Bitcoin client has been running for some three days now (with some sleep), and Task Manager says that it has written about 5,000,000,000 bytes so far, and read 3,800,000,000.  What exactly is it writing, and where, and why?

[Mike Hearn]

It records blocks and transactions into a database. So that is expected.

[bitcoinex]

My Bitcoin client has been running for some three days now (with some sleep), and Task Manager says that it has written about 5,000,000,000 bytes so far, and read 3,800,000,000.  What exactly is it writing, and where, and why?

It is wrote little but a lot of talking with other clients