You and me both, Tim! This is one of the best “RAC Reality” summaries I’ve
seen.
Clay Jackson
Database Solutions Sales Engineer
clay.jackson@xxxxxxxxx<mailto:clay.jackson@xxxxxxxxx>
office 949-754-1203 mobile 425-802-9603
From: oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> On Behalf
Of Tim Gorman
Sent: Friday, August 7, 2020 10:04 AM
To: niall.litchfield@xxxxxxxxx; Amir.Hameed@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: Oracle RAC on VMWare
CAUTION: This email originated from outside of the organization. Do not follow
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This is awesomely concise, and should be read carefully as a result.
Particularly awesome is the comment about "N 9s". I didn't initially
understand to what he was referring, but then I recognized the "we need five
9's availability" gibberish that management uses, a catchy phrase that means
little in practical terms. Instead, discussions about RTO (recovery time
objective) and MTTR are much more actionable, as Niall indicates.
Also amazingly awesome is the first bullet item about "RAC aware applications
... ONS events via TAF..." which is another hugely important point understated
wonderfully. Please be sure to comprehend all that is stated, because almost
everyone believes that a RAC database magically imparts transparent application
failover to applications by itself.
Thanks Niall! I'm so stealing this...
On 8/7/2020 7:42 AM,
niall.litchfield@xxxxxxxxx<mailto:niall.litchfield@xxxxxxxxx> wrote:
Hi Amir
We have run RAC on VMWare platforms ( a couple of different versions). My view
is that by and large implementing RAC on top of VMWare is usually done for the
wrong reasons (to migrate workloads as is and to consolidate workloads). There
are a few reasons why you might wish to run RAC.
* You have built RAC aware applications that can already respond
appropriately to ONS events via TAF, Application Continuity etc.
* You have a strictly low downtime tolerance in the event of failures - as
in downtime can be no longer than x seconds, not as in N 9s.
* You already run rolling upgrades/patching and don't want to lose that
ability or switch to standby first upgrades/patching
* Your workload is already larger than the largest physical machine you
have can cope with.
If the last one is your use case for RAC then the Oracle VMs won't be a great
size for a platform that's designed to enable efficiency among lots of
relatively small workloads. It's possible they'll be too large for the
underlying ESX hardware anyway. If you actually have a bunch of smaller
workloads that you wish to consolidate and you don't meet the criteria above
then it's probable that single instance (perhaps SIHA for automatic restarts)
is a better bet for you. It plays much more nicely with the VMWare architecture.
Some things you need to remember.
* You'll need to allocate thick provisioned multi-writer disks for the
database storage - this means that some VMWare features aren't available to you.
* You should ensure that you apply anti-affinity policies to make sure the
RAC nodes don't all end up on the same physical hardware!
* You'll need a specific private network(s) for your RAC clusters.
* You may well have added licensing headaches to deal with.
* VMWare admins are often big fans of overallocating CPU and Memory - this
tends to work very, very badly indeed with performance-sensitive database
workloads.
* RAC clusters often have high-performance SAN storage dedicated to them.
Virtualized databases tend to have shared (often lower performance) storage. If
your database application is extremely I/O demanding then a VMWare platform may
struggle. VMWare can help with identifying this.
On Thu, Aug 6, 2020 at 2:08 AM Hameed, Amir
<Amir.Hameed@xxxxxxxxx<mailto:Amir.Hameed@xxxxxxxxx>> wrote:
Hi,
Our data center is in the process of doing hardware refresh and their priority
is to move every physical server to VMWare VM. Currently, we primarily run
middleware and some single instance databases on VMWare but all databased that
are RAC’d are configured on physical servers. I believe that Oracle didn’t
certify RAC on VMWare until recently. I am reaching out to this DL to find out:
1. Are there folks on this DL running Oracle RAC on VMWare and what has
been their experience?
2. Are there any caveats of running Oracle RAC on VMWare?
Any feedback will be greatly appreciated.
Thank you,
Amir
--
Niall Litchfield
Oracle DBA
http://www.orawin.info<https://nam05.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.orawin.info%2F&data=02%7C01%7Cclay.jackson%40quest.com%7Cc8458cc735b34f99eb1708d83af410ac%7C91c369b51c9e439c989c1867ec606603%7C0%7C0%7C637324167207359792&sdata=wXG5whevRKBnu0XYpQ7BXIzZHO3Z%2FSAnVpWoubq8aCA%3D&reserved=0>
