Re: Multi-instances cluster and ASM max lun numbers

From: Robert Hanuschke <robert.hanuschke_at_gmail.com>
Date: Mon, 30 Jul 2012 17:08:53 +0200
Message-ID: <CAL6WDh2gESadYPOOiqur+32NLTO1wNWsfyekvyP2DoJy_0VNYw_at_mail.gmail.com>

Hi Stefano,
have you tested and experienced performance decreases when having combined DATA / FRA / REDO luns for several databases?

I run some clusters where up to 30 databases share the same disk groups - one for data, one for fra, 2 separate for redo log mirrors on faster disks - just separated by directories inside ASM (OMF). Not having any problems with it.
Would only consider adding more redo log luns on different physical disks once we experience I/O problems, the data disks do not show signs of too much load even during busy times.

This might of course be different in your environment, having applications that behave another way.
But I think it's worth checking if you really need 3 luns for every database you have. Even more so if those luns access the same disks on your storage system in the end.

Best regards,
Robert
http://robertvsoracle.blogspot.com

On Mon, Jul 30, 2012 at 3:30 PM, Stefano Cislaghi <s.cislaghi_at_gmail.com>wrote:

> Hi all,
>
> I have an interesting situation: a three nodes cluster (using oracle
> grid infrastructure) hosting about 20 instances.
> The cluster is acting as a normal failover cluster, each instance has
> 3 diskgroups (DATA, FRA, REDO) plus a lun for binary.
>
> This configuration is not usually described afaik even if it is
> working. An interesting thing is that ASM has a limit about max lun
> mounted: 64.
> With this configuration there is a huge limit, in case of a node
> failure both nodes might not be able to support everything. Also we
> have seen that when ASM have to mount 10 luns in the same time it is
> very slow.
>
> So, I am curious to understand how you would tackle with this problem
> and if you might use a different approach.
> Contraints:
> - RAC is not available due to money limits and too many applications
> not certified
> - Instances cannot be aggregated
>
> So any feedback is appreciated.
>
> Thanks
> Stefano
>
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> http://www.stefanocislaghi.eu
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Received on Mon Jul 30 2012 - 10:08:53 CDT