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1006886 wrote:"My comp" Is it means PC ? If yes, then I think you are using Desktop Virtualization tools for implementation Oracle RAC.
My comp is running with RAC 11gR2 with ASM on external redundancy. we are planning to move on normal redundancy.
There have not any mirroring on shared virtual disks. Then it is better use Normal redundancy for your ASM Diskgroups.
Did you have RAID on your Storage?
If yes, then not need mirroring on ASM disk, because mirroring is better on hardware.
which will be better normal redundancy or external redundancy.It is depend your storage configuration, if not any RAID, then you must use Normal or High redundancy for yoir ASM Disk groups.
Mahir M. Quluzade
ASM is not RAID. To say that you do not benefit from ASM if your storage is already mirroring data is wrong.
ASM is a software based implementation to provide data redundancy, but it is not RAID and works on the basis of file extents (AU units) distributed on available free space of disk failure groups. It knows about Oracle database files and uses an optimal stripping size based on file templates.
ASM, unlike RAID solutions provides more configuration and space management flexibility. For instance you can add disks without having to rebuild your RAID configuration. From a performance, redundancy and space utilization aspect, multiple ASM failure groups (single or multiple disks) can provide a better value for money than any RAID solution when using Oracle Database products.
ASM is a complementary product and may use devices that are a hardware RAID for additional performance and disk level redundancy. So is ASM with redundancy better than external redundancy: YES.