Relative storage newcomers like 3PAR have been challenging the Tier 1 manufacturers for years from a performance and scalability perspective. In many cases, their clustered storage controller deployments combined with advanced features like thin provisioning have proven a viable alternative to Tier 1 storage. Now the company is prepared to fully challenge Tier 1 storage vendors with advanced data availability features. This brings a hybrid category into focus that can be viewed as a unified ‘Tier 1+’ storage offering. Tier 1+ storage provides the performance and now the availability of Tier 1 storage, but does so with a Tier 2 cost structure and built-in virtualization to meet the flexibility needs of the new data center. 

When discussing Tier 1 availability, often the primary focus is several factors: non-disruptive upgradeability, a resilient architecture that can maintain service levels under a variety of failure scenarios and sophisticated multi-site, multi-mode disaster recovery. Service level maintenance and elimination of downtime are not just the goals of the very largest data centers, but also of many mid-tier data centers. A great example can be found in cloud computing where thousands of organizations are consolidated on a single architecture with variable SLAs. Such an architecture must be able to deliver Tier 1 service levels but offer cost effective service for Tier 2 data and maintain the flexibility that only a virtualized infrastructure can deliver. 

A typical Tier 1 storage deployment for disaster recovery, now made more accessible to more organizations thanks to Tier 1+, would be to synchronously replicate data to a close-by, within miles, secondary data center (Synchronous Site). In this scenario the secondary data center receives writes at the same time as the primary data center and a write commit is not given to the application until both sites have written the data. To maintain this consistency with reasonable application performance, the distance between the sites has to be kept to a minimum.

The challenge is that the close proximity that synchronous replication requires would not protect the organization’s data from a regional disaster, a power grid failure for example. As a solution, Tier 1 and Tier 1+ storage systems have the ability to asynchronously replicate the volume to a long distance data center (Disaster Recovery Site), with new or changed data sent hundreds or thousands of miles away. Synchronous replication over this distance could require a delay of a few seconds or minutes, depending on speed of the WAN connection, and therefore is not feasible. With asynchronous replication the application does not need to wait for the write to be completed and thus experiences no delay in performance.

The downside is that in this scenario the disaster recovery site may be out of sync if there is a sudden outage at the primary site. While applications can be brought online rather quickly there is typically some data loss, recovery and re-synchronization that would need to be done. In an environment where thousands of users or worse, thousands of businesses could be affected, the downtime to recover lost data and resynchronize applications is unacceptable.

To combine the benefits of both synchronous and asynchronous replication and address their respective limitations, the solution in Tier 1 and 1+ storage systems is to deploy a multi-site, multi-mode replication capability. In this implementation data is still synchronously replicated to a nearby synchronous site in real time. However, the primary site also asynchronously replicates data to a third disaster recovery site that is further away. This capability is limited to only a handful of Tier 1/1+ vendors--there are no Tier 2 storage systems that can accomplish this. What is unique here is the ability at the time of a primary data center failure for the array at the synchronous site to automatically push these changes in data or ‘deltas’ to the third disaster recovery site. As a result, the third site is in a data-consistent state with the primary and recovery can begin immediately.

Designing this robust type of disaster recovery strategy has traditionally resulted in systems that are complex, inflexible and generally unaffordable. Tier 1 storage is particularly well-known for its high level of professional services requirements. Implementations of the initial system can take months and the deployment of the complete disaster recovery strategy costs millions. Tier 2 storage, conversely, is known for a more attractive cost structure but is completely lacking in such advanced disaster recovery capabilities. Couple these with the flexible, rapid deployment model of virtualized infrastructure, which is often measured in days, and you have a new category of storage. Tier 1+ brings the flexibility and rapid deployment of virtual infrastructure and the cost-attractiveness of the Tier 2 world into a Tier 1 storage paradigm. Even sophisticated DR strategies like the multi-site, multi-mode deployment described above only add a few days, if that, to the overall deployment.

Finally, and potentially equally as important, is the cost structure of Tier 1+. The current economic conditions dictate that organizations spend precious capital wisely. This means that purchasing a Tier 1 system for performance or availability is out of most organizations’ reach. The effect is that customers could face lower performance, less robust DR protection, and array sprawl if a lesser Tier 2 storage system is selected where a Tier 1 was needed. This forces the organization into a difficult choice, neither option being particularly desirable. Tier 1+ storage eliminates this lose-lose choice. For about the price of an upper-end Tier 2 storage system, companies like 3PAR are able to offer a virtualized platform with Tier 1 performance and availability without complex and costly workarounds. Essentially Tier 1+ brings Tier 1 resilience with Tier 2 cost structure and the built-in virtualization that virtual data center deployments need.

George Crump, Senior Analyst

This Article Sponsored by 3PAR