Disk Arrangements

[sukishan]

Disk Arrangements
Efficient processing of the DBMS requests requires efficient handling of disk storage. The important aspects of this include:

- Index handling
- Transaction Log management
- Parallel Disk Requests
- Data prediction

With indexing, we are concerned with finding the data we actually want quickly and efficiently, without having to request and read more disk blocks than absolutely necessary. There are many approaches to this, but two of the more important ones are hash tables and binary trees.

When handling transaction logs, the discussion we have had so far has been on the theory of these techniques. In practice, the separation of data and log is much more blurred. We will look at one technique for implementing transaction logging, known as shadow paging.

Finally, the underlying desire of a good DBMS is to never be in a position where no further work can be done until the disk gives us some data. Instead, by using prediction, prefetching, and parallel disk operations, it is hoped that CPU time becomes the limiting factor.