The cloud has become the new computing cluster. Clustering – the ability to have two or more computer operate in lockstep for highly available systems — has been around since almost the earliest PC and mainframe days. But a new take on clustering is emerging that leverages virtualization tools and is becoming more appealing, particularly as enterprise IT shops gain more experience using virtual servers and as the cloud and virtualization vendors add more high-availability features to their products. The cloud is becoming the new way to provide redundant services, and as such is making it more affordable and within reach of businesses without a lot of IT expertise too.
PC Clustering used to be a very specialized discipline. You needed to set up nearly identical computers and run special operating system versions to keep them synchronized. They required special networking adapters to move data between the two PCs at very high speeds. But networks have gotten faster, so that gigabit or better Ethernet is now found on most desktops and servers. And a combination of services including high availability, virtual storage management and near-term server failover that were previously only the province of very expensive and customized clustered configurations are now available in the virtual world and can serve as a good substitute for many enterprise’s disaster recovery (DR) applications, too.
Certainly, the cloud is on the rise for many enterprises: a combination of better resource use, reduced data center costs, and more manageable applications delivery have made it a very popular solution recently. And as IT shops gain more expertise in delivering virtualized applications, they have seen that they can also get a better handle on how to leverage this expertise to deliver clustering solutions.
How has this happened? Virtual machines are easily portable and replicated across the cloud, so you can quickly get a secondary site up and running when the primary server has failed. “We have seen disaster recovery protection now available to a whole class of customers that couldn’t do it before,” says Bob Williamson, an executive VP with Steeleye Technology Inc., a specialized virtualization vendor. ”In the past, you needed to buy another physical server and have it ready if the primary machine went down. [The cloud] lowers the entry cost for deploying wider-area disaster recovery, and opens up this protection to a whole new set of companies that haven’t been able to consider it before.”
In the past couple of years, the major virtualization vendors have strengthened their ability to provide more capable DR and business continuity services in their products. Citrix has purchased VMlogix, which allows for more capable automated setup and tear down of multiple machine configurations and automation tools that can be used with multiple hypervisors from all three vendors. VMware has released its vFabrik and vCloud Director products. The former combines the Spring Java development environment (which VMware manages for the open source community) for a lightweight app server and load balancing and other infrastructure needs so that you can move things between various cloud instances. The latter can be useful for managing multiple virtual machines in the creation of a virtual datacenter and set up pre-configured app services and infrastructure.
Other vendors such as Novell have stepped into this arena with their tools to help automate the provisioning of new virtual machines and make DR easier. Novell’s Cloud Manager for example has automated, template-based provisioning processes that allow users to request, approve and deploy new workloads using a single Web-based portal. And its Forge appliance makes it easier to rapidly recover workloads with one-click failover and flexible restore options.
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Caption: Novell’s Forge appliance can recover workloads with a single click and with this dashboard, you can easily see the status of your virtual machines.
These solutions aren’t appropriate for transaction processing applications where immediate failover is required to handle things like online payments processing or airline reservations. “There are still times when you need more precise clustering, such as when you can’t afford to lose a single transaction and have to restart this transaction on the new machine after a failover,” says Carl Drisko, an executive and data center evangelist at Novell. “If your virtual machine goes down, anything that is being processed in memory is going to be lost.”
“If you are using some sort of transaction processing system where you need to preserve the state of the server, then you are going to need some special purpose clustering solution. But the majority of the applications in the data center don’t need this level of granularity, and you can get by with what we call the poor man’s high availability solution,” says Ken Oestreich, who is Cassatt’s Director of Product Management. Cassatt makes automation tools for managing virtualized sessions. But the high-availability virtualized applications can work for less demanding cloud-based line of business applications.
One of the issues with earlier custom clustering solutions is that they require identical hardware and operating system versions for each physical machine that was part of the cluster: the cloud is more forgiving and flexible, not to mention less expensive too.
Another issue is that many of the older-style clusters required very high-speed links to tie the members of the cluster together: cloud-based solutions are also less demanding of connectivity and can make do with longer latency connections, even across typical Internet lines. VM6 Software has a high-availability solution called VMex that runs on Hyper-V that can turn two PCs into a high-available cluster without the need for specialized hardware, even using ordinary Ethernet connections for less demanding applications. When the first Hyper-V machine fails, all the virtual machines will be brought up on the second machine automatically.
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Caption: Creating a storage partition using VM6 Software’s VMEx.
As these ‘almost-clustering’ solutions become more popular, look towards increasing sophistication of third-party monitoring vendors to help provide a complete solution.
All this means that clouds and clustering will become more interrelated and complementary solutions for IT managers. While the two technologies have come from different heritages and infrastructures, they are now merging and providing a powerful tool for managing more complex enterprise workloads and making them more appealing to smaller-sized businesses, too. “If you can afford the longer failover times for some of your applications, you can get a better level of resiliency and business continuity from virtualization and the cloud,” says Oestreich.