Oracle/HP Best Practices Guide for HP IO Accelerators

Redundancy architectures 7
Redundancy architectures
Redundancy best practices
When a failover system is not available to provide failure protection, all storage devices which are not
highly-available, including IO Accelerators, must be mirrored to provide redundancy.
Local redundancy is not as critical for designs that include both off-server replication and a hot standby
failover server ready to take over. However, local redundancy might still be used in some environments.
Filesystem hosted data files
If you use a filesystem to host the database data files, and no off-server replication is being used, HP
recommends that RAID 1 or RAID 10 be used over the top of the IO Accelerator. For instructions, best
practices, and tuning recommendations for setting up a RAID device and filesystem across multiple IO
Accelerators, see the HP IO Accelerator User Guide for your operating system.
ASM Mirroring
The following sections discuss various mirroring configurations.
External redundancy (striping/RAID 0)
In a RAID 0 configuration, ASM does not provide mirroring redundancy. It relies on the storage system to
provide any needed data protection. ASM can aggregate multiple IO Accelerator block devices into a
single disk group. All disks must be located to successfully mount the disk group.
The following command creates a disk group with four 320GB IO Accelerators, fioa through fiod,
resulting in a 1280GB disk group:
ASM SQL > CREATE DISKGROUP DATADG EXTERNAL REDUNDANCY DISK '/dev/fio[a-d]';
The following command creates a second disk group of four 320GB drives, fioe through fioh, each
down-formatted to 200GB for a total disk group size of 800GB.
ASM SQL > CREATE DISKGROUP LOGDG EXTERNAL REDUNDANCY DISK '/dev/fio[e-h]';
Normal redundancy (mirroring/RAID 1)
ASM provides two-way mirroring. By default, all files are mirrored so that every data extent has two
copies. A loss of one ASM disk in any failure group participating in the mirror is tolerated. A normal
redundancy disk group requires a minimum of two disk devices (or two failure groups). The effective disk
space in a normal redundancy disk group is half the sum of the disk space in all the devices.
This example demonstrates the creation of two ASM disk groups by mirroring the following device pairs:
• /dev/fioa to /dev/fioc