Why Deliver Subversion MultiSite as a Software Appliance?
The answer to this question is that software appliances reduce the cost and complexity of installation, deployment and maintenance to an extent that no other delivery model can. For this reason our customers have readily embraced it. Indeed, many of them have already implemented other enterprise applications as software appliances.
To understand why the software appliance approach makes such a significant difference, I’ll start by looking at the challenges posed by the other major implementation alternatives: traditional behind the firewall, and hosted software as a service (SaaS). I’ll then explain how the software appliance approach overcomes them, without sacrificing functionality or performance.
Traditional Behind the Firewall Implementations
When IT organizations implement applications, they’re faced with a number of challenges. First of all, there’s the overhead of performing routine maintenance, including manually applying patches and performing upgrades, maintaining system availability and dealing with backup and recovery. Third party components around the enterprise application add to this complexity. For example, in the case of operating systems there are literally hundreds of Linux distributions or distros as they’re called, as well as various flavors of UNIX. When the application is part of a software stack consisting of multiple components such as web servers, or databases and your staff has varying degrees of skill with these components, the potential for human error goes up dramatically. If patches are applied incorrectly to any of the components, problem resolution can become incredibly complex and lead to extended periods of downtime.
In the case of ISVs, their own development cycles can become longer, since they face many of the same challenges as their customers. In addition, it’s unrealistic to expect software vendors to QA every new release of their products on every platform, particularly when the solution is part of a stack dependent on other components. Software vendors are effectively forced to choose specific platforms to make their products available on, in order to avoid being faced with an unmanageable QA and support burden. The downside for the software vendor is that this has the effect of limiting the size of their potential market. In addition, the support burden can still be high, even when a customer implements on a supported platform, if any of the components are installed and configured incorrectly, or a patch gets applied incorrectly. If these issues crop up during an evaluation, the result can be a longer sales cycle at best, or a lost opportunity at worst.
Software as a Service (SaaS)
As an alternative to in-house behind the firewall implementations, many IT organizations have turned to hosted software as a service (SaaS) solutions. SaaS offers the benefit of immediate deployment. It also leaves the maintenance and support burden primarily in the hands of the solution provider.
However, many IT organizations don’t feel that the SaaS model is the best fit for some of their enterprise applications. This may include applications that require modification because of unique business processes, or applications that require integration with in-house legacy systems.
This had led some vendors to introduce a hybrid model that combines the hosted SaaS approach with application delivery as a software appliance. WANdisco will soon be announcing a partnership with Amazon to leverage their EC2 service to offer this hybrid model for our enterprise enabled Subversion solutions, including Subversion MultiSite, Subversion High Availability, and Subversion Clustering. This will give our customers a full range of deployment options.
Software Appliance
If the goal is to achieve the zero latency deployment and cost savings of SaaS, while at the same time maintaining the control, security and flexibility of behind the firewall implementations, the software appliance is the way to go.
A software appliance is a software application combined with just enough operating system (JeOS), a stripped down version of Linux designed to meet just the needs of the specific application, so that it can run optimally on industry standard hardware, or in a virtual machine. The result is that environmental dependencies are virtually eliminated. In the case of the Subversion MultiSite Software Appliance in particular, this has the effect of reducing installation and deployment across multiple locations to a matter of minutes. In addition, maintenance is made even simpler by the fact that access to an update server is provided so that updates are applied automatically to all sites where the appliance has been deployed, virtually eliminating any room for human error.
The one area of concern some critics point to in the case of the software appliance delivery model is performance. With the Subversion MultiSite Software Appliance there are no tradeoffs in performance or scalability. In fact, performance is often superior and scalability is much easier to achieve.
In the case of performance, with a virtual software appliance all of the components, including the operating system, are configured for the specific application and virtual machine environment. rPath’s JeOS, (Just Enough Operating System) takes the existing general purpose Linux OS, strips it down, and tunes it specifically to meet the requirements of the Subversion MultiSite Software Appliance and the supported VM that it’s installed on. This optimized OS, with its smaller footprint consumes fewer resources, and delivers superior performance than deployment under a traditional fat OS designed to run on multiple pieces of hardware and support a broad range of applications. The rPath team that built and now provides support for JeOS is uniquely qualified in this area, as it consists of Linux experts from the original brain trust that developed Red Hat Linux, Red Hat Enterprise Linux and founded the Fedora project.
In terms of the other components, the Subversion MultiSite Software Appliance includes an Apache Web server that has been preconfigured for optimal performance with Subversion MultiSite only. In many IT organizations that implement the standard Subversion MultiSite solution, the Apache Web server is often configured to support a number of applications, not just Subversion.
Recent developments are also making the overhead imposed by the extra layer of software introduced by the hypervisor a non-issue. For example, VMware’s vServices that provide direct access to the hardware infrastructure via device drivers. The applications receive services from JeOS, and JeOS communicates directly with the device drivers. Hardware manufacturers have also been implementing virtualization specific technologies to enhance performance for several years now. These improvements have taken virtualization to the point where any overhead it introduces may be completely submerged by limitations in network, storage or memory subsystems. In fact, some new virtualization solutions are even able to overcome memory and processor constraints built into many applications, delivering superior performance to what would be possible with a physical server implementation.
In the area of scalability, when additional system resources are needed to support increased user and transaction loads, traditional implementations can be more difficult to scale because the OS is closely tied in with the hardware. Virtual software appliances like the Subversion MultiSite Software Appliance can easily be moved to faster machines, even on the fly, using tools such as VMware’s vMotion and similar offerings from other vendors.
The answer to this question is that software appliances reduce the cost and complexity of installation, deployment and maintenance to an extent that no other delivery model can. For this reason our customers have readily embraced it. Indeed, many of them have already implemented other enterprise applications as software appliances.
To understand why the software appliance approach makes such a significant difference, I’ll start by looking at the challenges posed by the other major implementation alternatives: traditional behind the firewall, and hosted software as a service (SaaS). I’ll then explain how the software appliance approach overcomes them, without sacrificing functionality or performance.
Traditional Behind the Firewall Implementations
When IT organizations implement applications, they’re faced with a number of challenges. First of all, there’s the overhead of performing routine maintenance, including manually applying patches and performing upgrades, maintaining system availability and dealing with backup and recovery. Third party components around the enterprise application add to this complexity. For example, in the case of operating systems there are literally hundreds of Linux distributions or distros as they’re called, as well as various flavors of UNIX. When the application is part of a software stack consisting of multiple components such as web servers, or databases and your staff has varying degrees of skill with these components, the potential for human error goes up dramatically. If patches are applied incorrectly to any of the components, problem resolution can become incredibly complex and lead to extended periods of downtime.
In the case of ISVs, their own development cycles can become longer, since they face many of the same challenges as their customers. In addition, it’s unrealistic to expect software vendors to QA every new release of their products on every platform, particularly when the solution is part of a stack dependent on other components. Software vendors are effectively forced to choose specific platforms to make their products available on, in order to avoid being faced with an unmanageable QA and support burden. The downside for the software vendor is that this has the effect of limiting the size of their potential market. In addition, the support burden can still be high, even when a customer implements on a supported platform, if any of the components are installed and configured incorrectly, or a patch gets applied incorrectly. If these issues crop up during an evaluation, the result can be a longer sales cycle at best, or a lost opportunity at worst.
Software as a Service (SaaS)
As an alternative to in-house behind the firewall implementations, many IT organizations have turned to hosted software as a service (SaaS) solutions. SaaS offers the benefit of immediate deployment. It also leaves the maintenance and support burden primarily in the hands of the solution provider.
However, many IT organizations don’t feel that the SaaS model is the best fit for some of their enterprise applications. This may include applications that require modification because of unique business processes, or applications that require integration with in-house legacy systems.
This had led some vendors to introduce a hybrid model that combines the hosted SaaS approach with application delivery as a software appliance. WANdisco will soon be announcing a partnership with Amazon to leverage their EC2 service to offer this hybrid model for our enterprise enabled Subversion solutions, including Subversion MultiSite, Subversion High Availability, and Subversion Clustering. This will give our customers a full range of deployment options.
Software Appliance
If the goal is to achieve the zero latency deployment and cost savings of SaaS, while at the same time maintaining the control, security and flexibility of behind the firewall implementations, the software appliance is the way to go.
A software appliance is a software application combined with just enough operating system (JeOS), a stripped down version of Linux designed to meet just the needs of the specific application, so that it can run optimally on industry standard hardware, or in a virtual machine. The result is that environmental dependencies are virtually eliminated. In the case of the Subversion MultiSite Software Appliance in particular, this has the effect of reducing installation and deployment across multiple locations to a matter of minutes. In addition, maintenance is made even simpler by the fact that access to an update server is provided so that updates are applied automatically to all sites where the appliance has been deployed, virtually eliminating any room for human error.
The one area of concern some critics point to in the case of the software appliance delivery model is performance. With the Subversion MultiSite Software Appliance there are no tradeoffs in performance or scalability. In fact, performance is often superior and scalability is much easier to achieve.
In the case of performance, with a virtual software appliance all of the components, including the operating system, are configured for the specific application and virtual machine environment. rPath’s JeOS, (Just Enough Operating System) takes the existing general purpose Linux OS, strips it down, and tunes it specifically to meet the requirements of the Subversion MultiSite Software Appliance and the supported VM that it’s installed on. This optimized OS, with its smaller footprint consumes fewer resources, and delivers superior performance than deployment under a traditional fat OS designed to run on multiple pieces of hardware and support a broad range of applications. The rPath team that built and now provides support for JeOS is uniquely qualified in this area, as it consists of Linux experts from the original brain trust that developed Red Hat Linux, Red Hat Enterprise Linux and founded the Fedora project.
In terms of the other components, the Subversion MultiSite Software Appliance includes an Apache Web server that has been preconfigured for optimal performance with Subversion MultiSite only. In many IT organizations that implement the standard Subversion MultiSite solution, the Apache Web server is often configured to support a number of applications, not just Subversion.
Recent developments are also making the overhead imposed by the extra layer of software introduced by the hypervisor a non-issue. For example, VMware’s vServices that provide direct access to the hardware infrastructure via device drivers. The applications receive services from JeOS, and JeOS communicates directly with the device drivers. Hardware manufacturers have also been implementing virtualization specific technologies to enhance performance for several years now. These improvements have taken virtualization to the point where any overhead it introduces may be completely submerged by limitations in network, storage or memory subsystems. In fact, some new virtualization solutions are even able to overcome memory and processor constraints built into many applications, delivering superior performance to what would be possible with a physical server implementation.
In the area of scalability, when additional system resources are needed to support increased user and transaction loads, traditional implementations can be more difficult to scale because the OS is closely tied in with the hardware. Virtual software appliances like the Subversion MultiSite Software Appliance can easily be moved to faster machines, even on the fly, using tools such as VMware’s vMotion and similar offerings from other vendors.
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