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RE: Configuration of the SAN

From: Mark W. Farnham <>
Date: Tue, 29 Mar 2005 12:30:36 -0500
Message-ID: <>

So many possibilities, but I'll try to avoid my usual book.

Two quick thoughts:

  1. You bemoan "waste" in the lost acreage. One thing you can do with some of that acreage is more redo groups. If you want to maintain the ping-pong of arch versus lgwr, add them at the proper point in rotation and set them up odds and evens. This allows arch to fall farther behind in a burst before you gate and allows longer recovery within the online space without having to reference the archive destination.
  2. If you consider the price for your SAN drives and really could live effectively with 4 or 8 GB total, you might want to consider solid state drives rated for survival in abrupt power outages. (I only feel comfortable with sufficient on board tested battery power to make two independent copies of the memory contents to two separate on board disks when an outage is detected. You want to be sure this exceeds the reliability of your technology stack to your SAN.) In addition to probably being price competitive and a whole lot faster, this will remove commit writes to the redo from the race for SAN cache. If your management software allows you to set up writing to the archives *NOT* through the cache, then you avoid polluting the SAN's cache with write once traffic.

Good luck.


-----Original Message-----
[]On Behalf Of Luc Demanche Sent: Tuesday, March 29, 2005 11:41 AM
Subject: Configuration of the SAN


We are trying to do a good configuration of our SAN. Let's see that exemple.

EMC, with disk of 146G.
- one LUN of RAID-5 for data (4+1 disks = 534G)

Here is my question, about redo logs
- one LUN of RAID-1 for redo group 1 (2 disks mirroired = 146G)

I will have a filesystem of 146G to store my redo group of 2G .... what a waste.
Same thing for my redo group 2 and my archived log files ...

What is your LUN configuration regardinf redo log groups and archived log files ?

Thank you

Luc Demanche
Oracle DBA
(514) 867-9977

Received on Tue Mar 29 2005 - 12:37:04 CST

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