Judith,
We've have very very bad write latency on Oracle over Advfs (over 400
ms) due to write sequentialization on writes to a single file. This
was terrifically difficult to localize, but reading Oracle's write
time counters after building a new tablespace will give you a feel for
its impact in your configuration. I would certainly recommend that any
database that requires high write rates not be run on Raid5 or Advfs.
Their combination could really give you trouble particularly during
partial stripe writes.
If you must do this for cost efficiency I would spend some time
understanding your write load and optimizing your Raid5/Advfs/Oracle
for it. You may try to get a nice small stripe that minimizes partial
writes. I would also keep your Advfs domains down in size (to minimize
recovery time) and most critically I would never execeed about 100 MB
on a single data file. You will also need to run multiple database
writers as you can not run asynchronous IO.
The Oracle MetaLink pages are now filled with warnings on our
experience. Compaq acknowledges the problem and the write
sequentialization will be removed in a future release of the 5 stream.
-Brian Milnes
Systems Engineer
Amazon.Com
Received on Mon Mar 15 1999 - 04:06:29 NZDT