The Need for Variable Server Architecture


Most organizations today spread their applications across servers based on functional boundaries. Both large and small companies use email servers, file servers, Web servers and so on. Over time, the trend has been to dedicate a specific server for each function, using vendor-supplied appliances as required. An appliance allows for a relatively small footprint and also provides more of a plug-and-play infrastructure over the traditional server application experience, dividing the component parts across multiple appliances as necessary.


Maintaining a pool of idle servers on standby in case of increased load or for failure recovery can adversely affect the efficiency even further. Maintaining a homogeneous environment of appliances is extremely difficult. Adding to that is the need to upgrade at different times.


Virtual Appliances


A virtual appliance is one that subdivides the physical hardware into multiple virtual machines. Each virtual machine provides a self-contained appliance layer to the application. Virtual appliances can thus be distributed across the set of systems merely by transferring a virtual appliance image. Load balancing can be achieved between different servers with no need or requirement to physically move the appliance. The virtual image is simply transferred to the appropriate server.


Memory utilization, disk utilization and processor utilization can be more accurately balanced and controlled. By encapsulating each application in its own virtual appliance, the needs of that particular application can be tuned more precisely. Virtualization provides all of the benefits of the traditional appliance, with the following the key benefits:


  • Ease of evaluation and testing,
  • Ease of deployment,
  • Redundancy and backup, and
  • Scalability and mobility.

Ease of Evaluation and Testing


In order to evaluate a new appliance, the manufacturer must first ship a sample appliance to the evaluation tester. Once the decision is made to perform the evaluation, arranging for a sample appliance can often take up to two weeks before the appliance is available for testing. On completion of the evaluation, the sample appliance must then be shipped back to the manufacturer. Even in the event that the appliance is purchased, generally a new appliance will need to be shipped as the sample appliance will be "shop soiled" and unavailable for sale. Further to this, often it is a requirement of evaluation that the appliance be tested within the data center or at a remote geographic location. This adds further difficulties in installing and performing the evaluation as the tester must arrange for the appliance to be further delivered to the data center and installed.


Virtual appliances allow the user to load the virtualized image onto an existing server or desktop and begin evaluation and testing immediately. On completing the evaluation, the administrator or evaluator can simply remove the virtual image, and the system is restored to its original state.


At the completion of an evaluation, it is often essential to retain the test data or evaluation data for some period of time until decisions have been made by other teams or by senior management. In the normal case, this requires that the sample appliance sit idle until such time as it is free to be reinstalled and redeployed. In some cases, the manufacturer will request the return of the appliance before even the evaluator has had time to complete the evaluation. In the case of virtual appliances, old evaluation and test images can be saved to tape or another backup medium for future analysis or further testing, thus freeing up the test system for other tests. Similarly, the test system can be easily restored to a pristine state by the application of a new image, thus preventing cross-contamination of tests.


Ease of Deployment


Ease of deployment is a key requirement for any data center or organization. The ability to be able to migrate an image onto a new virtual appliance cannot be overstated. Each virtual image contains all the necessary components to deliver the required service or function. The image can be effortlessly deployed to any virtual machine anywhere.


Installing a new appliance in a data center or branch office can take days if not weeks. The hardware must be delivered in the first instance. Secondly, it must be pre-staged and then shipped to its eventual destination. It is often the case that the person performing the initial configuration or pre-staging is not the same person performing the physical installation. This can raise several issues. Most notably, changes in physical topography can render the pre-staged configuration obsolete. Also, it is often the case that the configuration must be performed by a specialist. This means that the physical appliance must be installed at the data center prior to the arrival of the specialist. It is possible to streamline this in large data centers, but it is still cumbersome and generally not available to smaller organizations.


By way of contrast, being able to deploy a new email security gateway such as SpamTitan simply by attaching the image to the virtual server application allows an organization to bring up the new security system in a matter of minutes instead of hours or even days. Utilizing a virtual server application decouples the server deployment and the deployment of one or more virtual appliances – this creates an immediate result.


Redundancy and Backup


It is essential in this day and age that organizations plan for the possibility of disaster, regardless of the size of the organization. Often, each appliance will have its own backup schema, making automation difficult if not impossible to restore redundancy, backup and disaster recovery. A virtual appliance encapsulates all of the required "bits" for that server in an image file. It is possible to back up the image file on a nightly basis and to automatically copy the image to an off-site facility using the Internet. As the appliances within the organization become virtual, the mechanism for backing them up becomes standard across all appliances.


It is also far easier to manage duplicated server applications using virtual servers. If the organization has five or six server applications such as an email security gateway, Web content filter gateway, customer relationship management (CRM) application and so on, replicating these applications can require five or six additional appliances. Using virtual servers, it is possible to replicate all of the server applications with as few as two physical systems.


Redundancy can also be a core requirement when an organization is geographically dispersed. Each branch office will require its own email security server, domain server and so on. Generally, distributing the applications to each of the remote offices will require a different appliance for each application. Virtualization is almost essential in this case, as it allows each branch office to deploy a single hardware system with multiple virtual appliances instead of multiple physical appliances. The head office administrator can thus spread the virtual appliance suite based on each appliance and based on demand rather than on geography. New servers can be deployed and load-balanced with virtual machines at each outpost based purely on real-time requirements.


Backing up a virtual image is relatively straightforward in comparison to backing up a live system disk. Being able to represent the entire system as a virtual image has many advantages, particularly in terms of nightly backups or in the event of a restore from archive. Should a given system fail, which is not at all unusual, the images which were backed up can be immediately redeployed on another virtual machine with little or no downtime. Another virtual server can be quickly instantiated with the saved image. By using virtual appliances, the availability of the system can be maintained without the need for expensive, redundant appliances or systems. Once the server has been repaired or replaced, the virtual machines can again be migrated off the temporary server with a minimum of fuss or downtime.


Scalability and Mobility


Organizations generally grow in size. However, they can also shift laterally with personnel from one department being redeployed to another department. This kind of growth can create considerable scalability headaches for the IT department. Effectively, demand for a particular server, such as the email security appliance, can grow dramatically overnight. Other influences, such as an increase in email due to a promotional activity or a sharp increase in spam due to certain spamming campaigns, can also increase the load on a given appliance. The ability to be able to increase the physical characteristics of the platform or migrate an appliance from one server to another larger one provides a fast and effective mechanism for dealing with demand. Being able to instantiate an additional anti-spam server can also assist with short-term demand and offers a fast route to load balancing.


Attempting to prebuild this type of architecture using only physical appliances can create considerable space and cost difficulties as it requires that the organization plan for the largest throughput and build it out accordingly. This also leaves no possibility to handle peak demand in a more rational way, by having additional capacity that can be deployed for specific tasks. For example, it may be that a given company has a large Web site promotion that is due to come to an end. In addition, the result of the campaign has resulted in a significant increase in email messages received. As the number of hits on the Web site starts to fall off, spare capacity can be redeployed to deal with the additional volume of inbound email by reconfiguring the virtual appliances or by creating additional instances of the email security appliance and removing instances of the Web site.


When a specific server needs to be taken offline for whatever reason, the virtual images executing on that server can be migrated to a new virtual machine without issues of platform version or operating system version.


Mobility is absolutely essential for the proper operation of an application group. It can be next to impossible to move a running user base from one physical appliance to another without significant downtime. In the case of mail antispam appliances, user configuration must be migrated, along with live mail data and quarantine files, blacklists, white lists and other elements of the configuration. For a large group of users, these characteristics are changing in a nondeterministic way and at an alarming frequency. Small companies and large alike will often schedule appliance transitions months in advance. The new appliance will be deployed for a month or two while the administrator tries to find a window to migrate the user base. For most companies, these windows fall on weekends when demand is low. However, many organizations find it difficult to find quiet periods, even on weekends. Again, mail is a good example. Users will often check their email on the road, from home and even on vacation. Removing the mail security appliance from the picture can result in clogged mailboxes in a matter of hours.


Being able to encapsulate the entire email antispam and antivirus appliance into a single image makes mobility and scalability a relatively trivial exercise. The image is simply removed from the old virtual server and redeployed on the new one. Within minutes, the user community is accessing their email on the new server using the same password and same features as always.


Appliances have, without a doubt, made an important impact into how organizations manage their application pools. They have allowed administrators to migrate from a strategy of one large server in the corner to multiple servers, one for each application. Monolithic servers have gone the same way as monolithic computers. Today, in a networked environment, interconnectivity is the essential ingredient. The systems are distributed based on load and based on geography.


Virtual servers bring this type of distributed computing to new heights. The ability to move applications between servers, either those colocated in the head office or in the data center, or those distributed throughout the branch offices, has become a key business requirement. With disaster recovery preying on the peaceful sleep of most business executives, the ability to quickly redeploy an application moments after its host server has failed solves many critical business issues.


Unquestionably, the new frontier of application deployment is that of the virtual server, where the physical hardware no longer sets the pace. Instead, the virtual machine provides a pliable, portable environment for all kinds of applications in all kinds of locations.


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