Oracle RAC on VPLEX now certified

Last week EMC announced that Oracle RAC on VPLEX stretched clusters is now officially supported and certified by Oracle!

News Summary:

 

  • Oracle has certified that EMC® VPLEX™ METRO in a stretch cluster configuration can provide Oracle Real Application Clusters (Oracle RAC) customers with an easy-to-deploy, active/active solution, as they transform from single- to dual-site environments.
  • Having passed Oracle’s rigorous testing standards, the EMC VPLEX METRO solution can enable Oracle RAC to be easily configured over extended distances while enabling simultaneous access to the same data at both locations.

This is the final step in a process to help customers that have been asking for true active/active support over distance for their mission-critical Oracle Database business processes.

For those who are not yet familiar with this solution, here is a small summary:

  • Customers have been in search for ways to survive datacenter failures (i.e. “disasters”) without the need to recover and restart the databases, in such a way that any component failure or even complete site failure would not lead to database downtime
  • This was not possible before except when deploying complex configurations based on host mirroring using Oracle ASM or a 3rd party volume manager. (note that competing storage virtualization products from other storage vendors also do not offer this full capability – even though their marketing might make it seem so)
  • EMC VPLEX offers this functionality which is now completely certified and supported by Oracle, and the solution avoids risk by making the stretched cluster deployment as easy as a basic Oracle RAC install
  • The VPLEX solution offers additional benefits including better performance, better recovery from issues such as component or link failures and offers a complete solution for the whole application stack, not just Oracle
  • Note that AFAIK this solution should also work for IBM DB2 (but I haven’t confirmed)

The full news release can be found here: http://www.emc.com/about/news/press/2012/20120517-04.htm

A full series of blog posts on this solution can be found here: https://bartsjerps.wordpress.com/category/vplex/

The VPLEX witness (the final component of VPLEX that made this possible) was announced last year at EMC World 2011. Typically we see the start of market adoption between 1 to 1.5 years after bringing new technology in the market. I am working on a few customers myself who are on the edge of starting a project with this, hopefully by the end of year we have a set of good customer references!

Update: The new white paper can be found here: http://www.emc.com/collateral/software/white-papers/h8930-vplex-metro-oracle-rac-wp.pdf

Update 2: VPLEX support mentioned (briefly) on Oracle’s website: http://www.oracle.com/technetwork/database/enterprise-edition/tech-generic-linux-new-086754.html

Update 3: Demos available on EMC Demo Center:

EMC VPLEX Metro for Oracle RAC Solution Overview
Oracle RAC with VPLEX Metro Site Failure
Oracle RAC with VPLEX Metro Solution Overview
Oracle RAC with VPLEX Storage Failure

If you’re a frequent reader of my blog you might recognize familiar pictures there ;)

Performance – The database stack

hamb-stackAs mentioned before, I frequently find myself in discussions around Oracle performance and how an Oracle database behaves on EMC storage. It turns out that often there is a lot of confusion on how the different layers interact with each other and very few people seem to understand the whole stack.

So I started a personal challenge to make a “one picture tells more than 1000 words” complete overview of the Oracle on EMC database stack.

I failed.

Turns out it’s nearly impossible to get everything in one picture without cutting corners.

So here is a simplified (and therefore incorrect) picture. It ignores certain complexities and is far from complete, and might even contain errors.

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Stretched clustering basics

Before showing my preferred solution for Oracle stretched high availability clusters, first some clustering basics.

Active/passive versus Active/Active clusters

NASA cluster

NASA cluster

Most clustering software is based on active/passive scenarios. You have a system (say, a database) that is running on a set of resources (i.e. a server, to keep it simple) and you have another system (a standby system) that is ready to run the system (failover) but is not actually running it at the same time.

An Active/Active system in general means both systems are active at the same time. There is some confusion as this can mean that the standby system is used for other processing (say, A is production and B is standby but currently running acceptance or testing environments).

By my definition, active/active clustering describes a cluster where all cluster nodes (systems) are processing against the same data set at the same time. There aren’t many products that can do this, especially in the database world. One of the few exceptions is Oracle RAC.

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Limitations of host-based mirroring for stretched clusters

For data mirroring, EMC SRDF is sometimes used in such a setup that both servers write to one location only (the “far” server writes across dark fibre links to the local storage). EMC has similar tools (Mirrorview, Recoverpoint, etc) for other storage platforms than Symmetrix.

srdf cluster

SRDF cluster with passive target

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Why use Oracle ASM for Oracle databases

I’ve been in discussions with some customers recently about what is the best way to store Oracle database data. Needless to say that the foundation should be EMC infrastructure of course, but apart from that, what kind of volume manager and/or filesystem works best for performance and other features?

There are many volume managers, and many filesystems available, more or less dependent on what hardware and operating system you run the database.

Some have a long track record, some are new kids on the block. Some are part of the operating system, others are 3rd party add-ons, for which you might need to pay licenses.

One way of storing Oracle database data is Oracle ASM.
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How to set disk alignment in Linux

As you might know, if disk partitions containing Oracle datafiles are not aligned with the underlying storage system, then some I/O’s can suffer from some overhead as they are effectively translated in two I/O’s.

If you want more info, google for “EMC disk alignment” and you’ll find plenty of information, explaining the issue.

Update 28-03-2013: I wrote a follow-up for this post describing the same thing for Linux (Red Hat / CentOS / OEL) versions 6. For that, you might want to jump straight to the new post as this one gets a bit outdated ;-)
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