"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@xxxxxxxxxxxxxxxxxx
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@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> on
behalf of Ram Raman <veeeraman@xxxxxxxxx>
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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