Question: I have EMC disks using
ASM shared storage. I want to set-up archivelog mode in RAC, but I
don't know if it is wise to use ASM because it used
Stripe-and-mirror-everywhere, with disk file striping. Does it make
sense to place archivelog on ASM (shared storage)?
Answer:
ASM uses RAID-10, striping and mirroring, not good for archive redo
logs. Plus, Oracle's OFA standard suggests that the
archive redo logs be duplexed on two separate disk spindles.
Remember, you NEED archive logs to roll-forward, and because ASM
stripes the files across multiple disk platters, a disk failure
would make it impossible to recover.
Also, all DML (insert, update delete) write to the
archivelog file, so you need it on a separate disk to prevent disk
I/O bottlenecks.
Instead, Oracle recommends duplexing your redo logs on two
separate, dedicated disk spindles.
Use EMC Symmetrics (or have EMC support) set-up two plain disks
for your archive redo logs, one for each RAC node.
Also, see these
related pages.
