An easy way to ensure redo logs do not cause I/O performance issues is to separate them from other database files. For example, because the I/O activity of redo logs is typically sequential and the I/O activity of data files is random, separating redo logs from data files improves performance. When you separate redo logs you should place them on the fastest devices available.
If redo logs are too few or too small, relative to the DML activity of the database, the archiver process must work extensively to archive the filled redo log files. Therefore, you must ensure that the redo logs are large enough to avoid additional checkpointing. Oracle recommends that you size the log files so that files switch every twenty minutes.