Re: SSDs and LUNs

"If there is a layer at which you have a single queue to each LUN you will have an I/O bottleneck" is exactly what I am thinking of. just 2 queues for TB of data?

Let me read up on the link Connor emailed.

Rich J: I cannot understand your question since those terms sound new to me. I will have to research that.

Mladen: It is going to be in house, not on cloud. and 1.5Tb LUNs are common (with SSDs?)? How is the IO in those installations? I understand that SSDs outperform HDDs, but I am wondering, just wondering, that by providing 2 or 4 luns we are losing the advantage that SSDs give us?

On Thu, Oct 19, 2017 at 1:39 AM, Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk
> wrote:

>
> At some layer between Oracle and the silicon the various software
> components will have some queues. If there is a layer at which you have a
> single queue to each LUN you will have an I/O bottleneck when you've got
> lots of Oracle processes trying to read from just 2 (or 4) LUNs.
>
> I'm not an expert with stuff that far away from the Oracle software but I
> would be a little surprised if you got bad performance because you were
> configured as 40 LUNs, while I have seen bad performance from a system
> where the solid state SAN had been configured as just 2 LUNs (one for data,
> one for redo).
>
>
> Regards
> Jonathan Lewis
>
> ________________________________________
> From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on
> behalf of Ram Raman <veeeraman_at_gmail.com>
> Sent: 19 October 2017 06:49:23
> To: ORACLE-L
> Subject: SSDs and LUNs
>
> We are moving one of the systems to vm. The consultants who have been
> hired to do the implementation are recommending that we create just 2 or 4
> 'LUNS' for data diskgroup for the db that is 3Tb in size which exhibits
> hybrid IO. They are promising it is best rather than having 30 or 40 LUNs
> since the new disks will all be SSDs.They are claiming that it will perform
> better than having 40 'LUNs'. I still have the 'old way of thinking' when
> it comes to IO. Can someone confirm one way or other, or point to any
> paper. thanks.
>
> Ram.
>
> --
>
>
>

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