Re: Oracle RAID

michael.pawle_at_ncom_main.ccmail.ncom.nt.gov.au wrote:

>How is ORACLE (v7.1.6) best configured on RAID5?
>What is ORACLE performance like on RAID5 compared to a conventional implementation over multiple disks?
>Should ORACLE's online redo log files and control files be mirrored on RAID5?
>Should ORACLE's archivelog mode be switched on at all (as RAID5 protects data from loss)?
>Would it be best to have a mix of RAID5 and non RAID disks so that log and control files can physically exist in 2 places?
>Where should Oracle Finacials out and log files be placed given a mix of RAID5 and non-RAID disks?
 

>I will soon have to install ORACLE (7.1.6) and Oracle Financials (release 10.5) on an IBM SP2 AIX box with 14 GB of RAID5.
 

>Thanks
 

>Michael Pawle
>michael.pawle_at_ncom.nt.gov.au

Under no condition would I run a high performance database at RAID 5, especially if you have a lot of INSERT activity. You are much better off using mirroring (RAID 1). If you MUST use RAID 5 for some tables, use it only for tables that receive very little update activity. Remember a RAID 5 update will write both the update and the parity information. This is two I/Os and although interleaved, less than desirable.

Secondly, redo log activity should be isolated from your data and index files. Never use redo logs and data or index files on the same

devices. This is because redo logs write synchronously ( O_SYNC) while other Oracle writes to the database via DBWR use ether async IO or list IO.

These are lessons we learned the hard way, I hope it helps.

We have been using redo logs on internal disks and oracle to mirror them (groups) and putting data files on their own RAID 1 devices and isolating index files on different RAID 1 devices with great success.

Dave Received on Wed Aug 23 1995 - 00:00:00 CEST