Richard Elling wrote:
On Sep 24, 2009, at 10:30 AM, Javier Conde wrote:
Hello,
Given the following configuration:
* Server with 12 SPARCVII CPUs and 96 GB of RAM
* ZFS used as file system for Oracle data
* Oracle 10.2.0.4 with 1.7TB of data and indexes
* 1800 concurrents users with PeopleSoft Financial
* 20000 PeopleSoft transactions per day
* HDS USP1100 with LUNs stripped on 6 parity groups (450xRAID7+1),
total 48 disks
* 2x 4Gbps FC with MPxIO
Which is the best Oracle SGA size to avoid cache duplication between
Oracle and ZFS?
Is it better to have a "small SGA + big ZFS ARC" or "large SGA + small
ZFS ARC"?
Who does a better cache for overall performance?
In general, it is better to cache closer to the consumer (application).
You don't mention what version of Solaris or ZFS you are using.
For later versions, the primarycache property allows you to control the
ARC usage on a per-dataset basis.
-- richard
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Hi
addign oracle-interest
I would suggest some testing but standard recommendation to start with
are keep zfs record size is db block size, keep oracle log writer to
it's own pool ( 128k recordsize is recommended I believe for this one ),
the log writer is a io limiting factor as such , use latest Ku's for
solaris as they contain some critical fixes for zfs/oracle, ie 6775697
for instance. Small SGA is not usually recommended, but of course a lot
depends on application layer as well, I can only say test with the
recommendations above and then deviate from there, perhaps keeping zil
on separate high latency device might help ( again only analysis can
determine all that ). Then remember that even after that with a large
SGA etc, sometimes perf can degrade, ie might need to instruct oracle to
actually cache, via alter table cache command etc.
getting familiar with statspack aws will be a must here :-) as only an
analysis of Oracle from an oracle point of view can really tell what is
workign as such.
Enda
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