Availability 
Using the appropriate hardware, operating system, or database features can improve the downtime security of a database instance.
In a production system, the log area should
always be mirrored for security.
Use hardware-based methods to mirror the log area. If this is not possible,
you can set the log mode of the
SAP DB database system to use software-based methods for the
mirroring.
Operate the log volumes in a RAID-1 configuration, since the database instance writes the log entries sequentially.
In a production system, always stick to standard log backups, and never deactivate redo log management, even if you use RAID systems for the data volumes.
If you wish to ensure a high standard of availability, we recommend using RAID-5 or RAID-1 configurations for the data area. A disk crash and change will then not affect the running of the database, if the RAID system is able to carry out a recovery.
Every volume category should be stored on a different disk.
When using fault-tolerant hardware, it is best to only use the same type of hardware when you want to extend the capacity. For example, RAID-5 systems should only be extended using RAID-5 systems and mirroring disks with mirroring disks.
UNIX: In a production system, data volumes and log volumes should be used in conjunction with raw devices. Raw devices achieve better performance, and are more secure in the event of a system failure.