How important is disk type for Oracle database files?

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Choosing the best suitable storage disk for your Oracle database is very important when you architect the environment for better performance. Not just considering database files (Data files, Control files, Redo logs, Archive logs etc…) it is also vital to look at the type of application and the data flow in and out of the database before opting a storage disk. We have seen how important are kernel parameters for better database performance similarly, right storage type will also aid in improving database performance. There are multiple types of applications categorized based on data flow like Online Transaction Processing (OLTP), Online Analytical Processing (OLAP), Loading(ETL), decision support systems (DSS) and so on. Choosing a disk type for each such environments will be completely different.
Example – A storage disk for your data files on OLTP environment will not perform well for data files on OLAP environment.
In this blog, we will discuss on: What RAID storage will be the best option for database files on OLTP and OLAP systems.
Widely used RAID types:
Features/RAID
RAID 0
RAID 10
RAID 50
RAID 5
Write performance
High
Medium
Medium
Low
Read performance
High
High
High
High
Data protection
No
Yes
Yes
Yes
Disk usage
100%
50%
67% to 94%
67% to 94%
Cost
Cheap
High
Very high
High
There are technical and non-technical factors to decide the appropriate storage for database files. Technical includes performance, data protection, Usage levels, reliability and so on. Non-technical includes vendor, disk costs, disk wastage, maintenance costs and so on.
When we merge all these factors, then choosing a storage disk might be different from what we are about to discuss. However, in this blog we consider that storage should have the best performance and data protection and see how to pick from the available RAID groups.
Environmental comparison:
Database files
OLTP environment
OLAP environment
Data files
Read and Write operations
More Read than Write
Redo log files
More Write than Read
Very less Write/Read operations
Archive log files
More Write than Read
Very less Write/Read operations
Control files
More Write than Read
Very less Write/Read operations
The above comparison is for business hours with respect to the storage disk I/O operations. We are not considering the behavior in non-business hours at the moment which includes data loading, backups, running scheduled jobs in the database, data maintenance etc…
Storage disks:
Database files
OLTP environment
OLAP environment
Data files
RAID 10
RAID 5
Redo log files
RAID 50
RAID 10
Archive log files
RAID 50
RAID 10
Control files
RAID 50
RAID 10
Key points:
  • Disk performance will vary from vendor to vendor like EMC2, IBM, DELL etc… We have discussed our scenario of choosing RAID groups taking any one vendor provided disks in the storage array.
  • Choosing storage disks are subject to change with non-technical factors as well.
  • We have not considered the behavior of database in non-business hours in this blog, so add it as a part of your analysis when you need.
  • There are complex RAID groups with E and EE extensions like RAID 5E, RAID 5EE that can be considered with proper assistance from storage administrators.
  • Focus on the block size of RAID group as well for better database performance especially for data files.
For more details on RAID levels – https://en.wikipedia.org/wiki/Standard_RAID_levels

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