On the other hand, LUN sizes of 1.5 TB are common. There is less
administration to do on the Linux side and 1.5 TB of flash drive will
outperform any rotational storage, simply because SSD is newer and
better technology. What I am unclear is what do you need ASM and RAC in
the cloud for? RAC requires application adjustment and if the cloud goes
out, which has happened, all of your machines go out. A standby in a
different zone would make much more sense.
Regards
On 10/19/2017 02:39 AM, Jonathan Lewis 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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