Re: RAID help

Joga,

You did not tell us the exact nature of your application (OLTP, DSS, Hybrid). Also there was no mention about the amount of memory configured on the machine, maximum number of concurrent users, size of the database, availability requirements,etc.

But given the number of drives that you have(4), I am almost tempted to ask you to break up the existing configuration and do not implement any RAID at all. You may have better luck dealing with your I-O problem by just using them as 4 individual disks.

We do not have much room to play and just striping across the 4 disks and creating 1 RAID 1 volume, will not work optimally as you will encounter significant contention amongst the various components of the Oracle database. If you get yourself 4 more disks (which you said that the client is unwilling), then at least you will have some options. But your options are pretty limited with the number of disks that you currently possess. If the application is write-intensive, then moving away from RAID5 will help in I-O performance, as the overhead posed by the "error correction control" parity algorithms can be avoided.

You better document the configuration and its inherent risks and educate everyone involved, so that everyone is singing the same song from the same page. Otherwise, your "rear" will be on fire, when this system experiences its first media failure. Put that DB in archivelogmode and get some hot backups going buddy.

Best Regards,

Gaja.

• Joga Rao Nakka <joga_at_paradise.net.nz> wrote:
  > I got a problem. I was asked to tune the database as its
  > performance very poor. Here is the existing database layout.
  >
  > Machine : IBM Netfinity 5500 M-20 with 2 x 550MHz processors.
  > disks : RAID5 disk array with 4 x 9.1 gigs (net 27 gigs)
  > with additional scsi channel connected to DLT tape drive
  > external
  > OS : WinNT 4.0 service pack 6
  > Oracle : 8i standard edition with one 8k block instance
  > Application: web application through Story server
  

> The entire disk array is made into 2 logical drives. 5 gigs
> and 22 gigs OS and Oracle is installed on small logical drive
> and Data ,index,
> RBS, TEMP, LOB tablespaces ,exports, REDOs and Archive logs
are > on 22 gigs logical volume.
>
> I advised the client to replace RAID5 with RAID0 + 1.
> Unfortunately Hardware does not support. IBM guy clarified >
this.
>
> The client does not want to spend any amount for additional
> disks.
> I left with two options :
> 1. To go for IBM enhanced RAID1 (striping + mirror)
> 2. Live with RAID5
> In the above cases, Please suggest me for suitable database
> layout which will give improve present bottleneck of disk I/0
.
> Before tuning RDBMS and SQL, I would like to come to
> baseline compromise with database layout.
>
> Does any one had came across RAID Enahanced 1 ...?
>
> I am new to Win NT on these boxes and RAID technology. Your
> help is very much appreciated.
>
>
> Regards
> Joga
>
> --
> Author: Joga Rao Nakka
> INET: joga_at_paradise.net.nz

Gaja Krishna Vaidyanatha   | 3460 West Bayshore Road,
Manager - Integration      | Palo Alto, CA 94303
& Consulting Services      | gaja_at_brio.com
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Brio Technology            | www.brio.com 

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