Thomas Kyte <tkyte_at_oracle.com> wrote in message news:<a9ve4f01cjv_at_drn.newsguy.com>...
> Our goal is to achieve even distribution across all devices. If in your case,
> the best you can do is put index on one -- table on another -- thats great. In
> general, putting index separate from data won't do that (achieve a balance).
> Striping and other technologies will.
Even distribution may not be always the main goal. Sometimes we even
want the exact oposite - isolating some heavy load on a ew devices.
For example some heavy workload - backup, export of data, adding disk
to array. Maybe we do not care how long this takes, but very important
can be to minimalise negative impact on response time for ordinary
users. Of course, access to data in the same tablespace/same disc is
very slow, but other parts of database has no problem with this heavy
I/O. If we've used an all drives stripping method, then every single
tablespace will suffer with this I/O.
Or partitioning issues. For example historical data and current data
in one database. Current data are heavily accessed and we want no time
response to them, historical data are used by some analytics for
extensive queries. They can (and must) wait, so high I/O is no problem
for them, but online clerks needs a low I/O to get data ASAP.
Recovery from HW can be another problem. If some disk needs to be
replaced, then while using smaller sets, we would also have a quickier
rewriting of data to a new one.
So I think that even with all great technologies (like striping, array
caching, ...), very careful placing planning is still an important
part of DB design.
--
_________________________________________
Dusan Bolek, Ing.
Oracle team leader
Note: pagesflames_at_usa.net has been cancelled due to changes (maybe we
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Received on Mon Apr 22 2002 - 09:57:13 CDT
