ASM in a non-RAC environment

Question

Gurus,
what are the advantages, if any, of running ASM in a non-RAC environment?
Thanks.

Answer 1

Any raid (that actually provides multiple disks in a
LVM) will nullify the performance gains of raw that
are associated with disk head contention.
Any disk subsystem with front-end RAM cache will
nullify the rest of the performance gains of raw
disk.
Any 'RAID-5 is good' argument under a database
assumes large and efficient cache.Unfortunately, we can't just discount RAID-5, since it is far too cost-efficient an option these days, with 10, 20, 30+ TB databases. Plus, the storage vendors actually make it efficient enough that it performs almost as well as RAID 1+0.
Multiple disks on the storage subsystem and RAM caches (for reads and writes) are still important and valuable performance enhancements. Remember that your storage subsystem is much more efficient at this than your database or server (since it's designed to do it!). True, it doesn't have knowledge of the database files, their content, and their usage, but you do, and can therefore intelligently configure the subsystem and place the data files.
ASM does nothing more intelligent than stripe the data across all of the available disks. The best part about it is the ability to dynamically grow the groups. The problem with it is that it thwarts the read-ahead cache of the storage subsystem. And, while Oracle will intelligently 'read-ahead', it can't optimize where the heads are on the disk, or take into consideration the 10 other servers accessing the same storage subsystem.
The problem with ASM doing the striping is that, for large databases, you will typically have hundreds of disks underneath the covers. If you gave the OS and then Oracle that many devices, what do you think would happen? It would step all over itself and seriously impair your ability to access the devices in parallel. Whereas, if you group 4 or 8 devices together, the storage subsystem will access them together in parallel for the OS.
So, don't discount your storage box... But yeah, use RAID 1+0 rather than RAID-5 (4,3) when possible!