hi,
This is what is recommended (raid 0 = stripes, raid 1 = mirrors, raid 5 = striping+parity):
A. no raid, raid 0 or raid 0+1 for online redo logs AND control files.
You should let Oracle multiplex them even if you mirror them. There are more opportunities for failure if the raid subsystem reports a "warning" back to us -- if we have multiplexed them -- we are OK with that.
B. no raid or raid 0 for temporary datafiles (used with temporary tablespaces). no raid/raid 0 is sufficient. If you lose these, who cares? You want speed on these, not reliability. If a disk fails, drop and recreate temp elsewhere.
C. no raid, raid 0 or raid 0+1 for archive. Again, use Oracle to multiplex if you use no raid or raid 0, let the OS do it (different from online redo log here) if you use 0+1.
D. raid 0+1 for rollback. It get written to lots. It is important to have protected. Oracle cannot multiplex them so let the OS do it. Use this for datafiles you believe will be HEAVILY written. Bear in mind, we buffer writes to datafiles, they happen in the background so the poor write performance of raid 5 is usually OK except for the heavily written files (such as rollback).
E. raid 5 (unless you can do raid 0+1 for all of course) for datafiles that experience what you determine to be "medium" or "moderate" write activity. Since this happens in the background typcially (not with direct path loads and such) -- raid 5 can typically be safely used with these. As these files represent the BULK of your database and the above represent the smaller part -- you achieve most of the cost saving without impacting performance too much.
Try to dedicate specific devices to
- online redo
- archive
- temp
they should not have to share their devices with others in a "perfect" world (even with each other).
hope this helps!
Regards
Yogeeraj
No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
