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An Oracle blog about Openomics

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    May 23, 2011

Leveraging a disaster recovery site for development - Part 2

Guest Author

In our previous post, we introduced the idea of using Disaster Recovery (DR) sites as a private cloud for hosting virtual development and testing environments. The solution we developped for an ISV partner of ours in the Healthcare sector looks like this.

Architecture

The solution is based on the Zones and ZFS features of Oracle Solaris --available from Solaris 10 and up. Solaris Zones
(a.k.a. Containers) are an operating system level virtualization
technology that provides a complete, light-weight and isolated run-time
environment for applications. ZFS is a new kind of filesystem that
provides simple administration,
transactional semantics and immense scalability; it also embeds advanced fonctionnalities in compression, encryption and snapshot, typically expected from proprietary high-end storage systems.

A ZFS snapshot is a
consistent point-in-time image of a filesystem. A clone is a writable
copy of a snapshot. Solaris creates ZFS clones quickly using no
additional disk space to start with, because data is not duplicated on disk unless/until the cloned image changes that data. Combined with Solaris Zones, ZFS Clone allows to provision almost instantly a Virtual Image (VM) of Solaris. This is what is at work here.

So, how does the overall solution work exactly? Data
is replicated between the production system and the DR site. The
replicated data is stored on the high-performance fiber-channel
drives, but is also duplicated, once, on low-cost high-capacity SATA
drives, managed by the same array head. A
Solaris Zone --we call it the “golden image”-- is created with the
software stack needed by the developers fully pre-installed and
configured: Web server, application server, database instance,
compilers, version controlling system, you name it. This
one-time installation and configuration work will be used as a
template for all development environments to come, thanks to the
cloning mechanism.



For
each new development VM, the golden image is simply cloned with a copy of the production data. When logging into the VM, the developer views it as a fully-independent Solaris
server, with its unique hostname and IP address, its own database
server running and fed with fresh production data that can be
read/updated/deleted with no restriction --remember, it is only a
clone. A
major point is that, once a template is set --many different templates
can be created--, cloning and booting a new virtual server is a matter
of seconds. As for the storage footprint, it will start from being
almost null, since a clone will only store changes that occurs during the
lifetime of the server.

Finally,
when an environment is no longer needed, deleting it completely
without leaving any trace is again a matter of seconds. For
a developer, this is a huge benefit; you can try something
completely crazy, no worrying about ruining your
environment and data. Create a server, test it, break
it, throw it away and create a fresh new server, all day, all you want!

To
summarize, the combination of the Solaris Zones and ZFS technologies fully addresses the requirements of our specs, and more :

  • Solaris Zones assure a total isolation between the development environments and the

    replicated production data, and between each development

    environment. To play it safer, the

    addition of low-cost SATA drives to store the test data

    assures a hardware isolation from the production replicated data.
  • The creation/deletion

    of a development environment is extremely fast, can be scripted, and

    can be based on different templates with different software

    stacks and/or configurations. Once a Solaris zone is created and

    configured, it can be used as a template and cloned to create new

    zones. Different templates can coexist.
  • Fresh

    data is constantly available to each development environment, with minimum storage

    footprint. With ZFS Clone, we work around the (impossible) need to duplicate large production databases, which is long and storage-space consuming.
  • A

    simple script can shutdown all zones (other than the global zone) is a

    handful of seconds, giving back all available resources (CPU,

    memory, network) to the DR system. It gives a quick

    and easy way to stop all development environments if a disaster

    occurs on the primary production site, so the DR site can take over.
  • Solaris Zones can be detached, exported and attached to another hardware

    server as long as you stay on the same hardware architecture (SPARC

    or x64) and OS level.
    This gives the ability

    to save/export a development environment to another server.

Two
last points are worth mentioning:

  • In

    this specific case, all environments were set to use the same Oracle

    11gR2 database binaries, installed in the global zone and shared by

    all local zones. However the isolation offered by a zone allows the

    installation of various versions of a same software in different

    zones. We can therefore imagine many other use cases; e.g. an

    ISV can keep a copy of each of its customer's environment in a zone

    for support reasons, or perform Q&A on new versions of third-party software.
  • Functional

    tests may pass successfully, without giving indications on how a new

    or updated functionality will perform once in production. One last

    benefit from using the DR site, which has often the same horsepower

    than the production site, is to do performance tests of a new or

    updated algorithm or SQL query. However, if the given test is

    susceptible to change the data, a snapshot should be taken before,

    to be able to rollback to the initial state, and obviously the

    replication should be stopped before and restarted after the test.

Now, what could Solaris Zones and ZFS do for you? If you're a Solaris ISV, let's talk!


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