Re: Server shared as a file server
- From: Dennis Williams <oracledba.williams@xxxxxxxxx>
- To: dcosta@xxxxxxx
- Date: Fri, 20 Jan 2006 12:44:52 -0600
Dias,
> Yes the database is critical. It's an ERP.
> No there's no the possibility of separating the I/O.
I think you need to point out to management that the ERP is likely to
run more slowly. Mention the paychecks might run late and see if that
gets their attention.
> And, if memory serves me well, i read somewhere
> that the two different regimes of reading from the
> disks may provoke latency.
Disk latency is the delay experienced when the disk head must be
repositioned to another track and then wait for the platter to rotate
the needed data underneath it.
In the old days when disks were expensive and people were cheap,
people would sometimes place data on specific locations on the disk.
The IBM mainframe, for example, let you specify physical disk
locations.
Don't worry about this specific issue. A relational database by
its nature reads data from a variety of tables and indexes. It
continually has the disk heads jumping all over the place. RAID makes
any rules of thumb much less reliable. But I/O subsystems often have a
cache (make sure it is battery-backed), which can help an Oracle ERP
system a lot. My guess is that a file server gets a wide range of
requests, and doesn't benefit much from the disk cache except
buffering the writing. Anyway, the combination of both applications
might result in Oracle getting little benefit from the I/O cache.
I would concentrate on the fact that Oracle imposes a challenging
load on an I/O subsystem, and a file server also imposes a challenging
load. Together the result may not be good. People get testy when their
paychedk is late.
Dennis Williams
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