All Oracle data files reside on storage media or devices, and storage management is a key part of Oracle database operations.  Typically storage means fixed disk drives or disk subsystems such as JBOD (Just Bunch Of Disks) or RAID (Redundant Array of Independent Disks), but storage can also mean non-volatile storage, solid state disk, removable storage, optical storage, or tape devices.

Storage related issues can impact Oracle database significantly in the following areas:

• Data Availability and Integrity
• Performance
• Manageability

Data Availability and Integrity

Even though today's disk drives are more reliable than ever with MTBF (Mean Time Before Failure) approaching one million hours, their mechanical nature still makes them more vulnerable to failure than other solid state components in a computer system.  This is especially true when there are hundreds or thousands of disk drives involved, which is not uncommon in today's data intensive ebusiness world.   When the storage is offline, the system or business is offline; the competitors are just a click away. 

There are storage solutions that address some of these problems, such as software or hardware RAID products that can keep a storage system, hence Oracle, up and running even if an individual disk drive fails. 

In a mission critical environment, data integrity is even more important than data availability.  Storage media, cache, or controller failure that causes data corruption can be worst than a failure that causes storage to be offline.   For example during a routine backup operation, corrupted data blocks caused by media failure may be copied to tape without detection -- until it's too late.  Oracle can check for data integrity before backup.  

Improper storage system design can also cause Oracle problems.   For example, if a storage subsystem allows asynchronous write to a data file before the log, Oracle database may become inconsistent and not usable.

Performance

Oracle performance is very I/O dependent; the faster Oracle completes an I/O the faster database runs.  Since data retrieval from the storage subsystem takes much longer time than data retrieval from system memory or cache, some intelligent storage subsystems try to minimize amount of time Oracle spend on an I/O by pre-staging data in memory or cache or reducing I/O wait time with non-volatile write back cache.

High level storage management functions like disk stripping or mirroring can also improve database performance by reducing hot spots on disks and allowing Oracle to access data in parallel.   Another function that can enhance performance is serverless backup, where storage devices can communicate with one another and transfer data without interrupting system CPUs or affecting Oracle Database Server.

Manageability

As storage becomes more central to ebusiness, the growth in storage capacity and complexity has been tremendous.  Heterogeneous, multi-terabyte, storage-centric sites are not uncommon these days.  Moreover, many Oracle customers are implementing many new and emerging storage technologies, such as Fibre Channel, Network Attached Storage (NAS), and Storage Area Network (SAN.)  Managing Oracle successively in such dynamic environment can be challenging, but fortunately Oracle is becoming more storage aware and is adding new features to address some of these issues.   For example, Oracle's new online data reorganization capabilities allow database administrators to move tables and indexes from one storage device to another without having to take the database offline.  Oracle Recovery Manager (RMAN) can handle backup and recovery for multiple databases.

Oracle is also working with all the leading system and storage vendors to make sure that their storage products work as seamlessly as possible with Oracle database through design reviews, joint API development projects, and compatibility programs.

Oracle and Storage Products

As a rule, Oracle does not certify or support third party storage products (disk, RAID, tape drive, HSM, etc.)  Oracle assumes the underlying storage solution is reliable, and the storage vendors support their products directly.  Oracle also does not recommend one vendor's solution over another's, we encourage Oracle sales people to find the best storage solution available for their customers.