Integrating PCIe SSD Into The Storage System

The NexGen storage system is designed from the ground up to take advantage of solid state storage and is the first system that we know of that integrates storage tiering from the first release. It is also the first storage system to use PCIe SSD for its solid state tier instead of using drive form-factor SSDs. This architecture provides the storage controller direct access to the high speed tier, removing the latency inherent in traditional SAS or SATA backplane networks.

The demand for cost-effective high-performance storage certainly exists. Database applications, e-mail environments and especially virtualized server and desktop infrastructures all are taxing mechanical hard drives to their absolute limit. The challenge though, is in implementing flash so that the budget isn’t broken.

In order to get to market quickly and meet the demand for flash-based performance, legacy storage vendors have quickly adopted drive form-factor SSDs that easily plug into their existing storage shelves. While this format for flash-based storage could be called ‘market efficient’ it’s not cost efficient, space efficient or even performance efficient.

Legacy storage vendors have now added automated tiering features that allow blocks of data to be transparently moved between the hard disk tier and the SSD tier. For almost all of these vendors automated tiering is more of an afterthought and as a result, may not be as efficient as if it was built from scratch into the storage software.

NexGen takes a different approach on both counts. Instead of using hard disk form factor SSDs they chose to integrate PCIe-based solid state storage into the storage head itself. This brings several immediate benefits to the user. First, it provides extremely high performance since the PCIe SSD has direct access to the storage controller and does not need to go through a backend network to communicate to the storage devices.

Compare this to legacy storage systems that have SSDs installed where drive shelves have to communicate through their standard storage network, which quickly becomes a bottleneck. As a result it’s not uncommon to see vendors provide SSDs in half populated shelves so that the connection between the shelf and the controller does not become overwhelmed by the I/O capabilities of the flash-based drives.

Secondly, additional performance now can be installed directly into the storage controller without increasing its footprint requirements. Again, each additional PCIe card continues to have direct access to the controller.

Legacy vendors, on the other hand, have to either put multiple SSD drives in the same shelf, which again exposes them to potential bottleneck issues, or provide half populated shelves as described above. This forces the customers to choose between subpar SSD performance or an extremely expensive deployment model. The NexGen solution allows for in-box scaling and direct high-speed access to the solid state technology, both of which should lead to more cost-effective, higher performing deployments, with much less complexity.

The second important innovation from NexGen is that their tiering software has been integrated into their storage software from the very beginning. It’s not bolt-on or add-on as most of the legacy vendors have done. This allows for more efficient data transfers and once again, thanks to the choice of PCIe SSD, higher performance.

The third key innovation is something that NexGen calls “deterministic performance”. This allows the storage manager or application owner to set performance on an IOPS basis for each individual application. For example, an environment that might have an Exchange server, an Oracle server and a file server can have performance levels preset for each server. The exchange server may have a policy that indicates it should always have 25,000 IOPS of performance. The Oracle server may require 50,000 IOPS and the file server may not need much performance at all, so it may be set at only 10,000.

With the NexGen software you essentially dial-in each application’s IOPS requirement. This means users now have the ability to set quality of service levels for each individual application in the environment, greatly simplifying performance management of the data center.

The next innovation was found as NexGen implemented its capacity optimization technology. Instead of using a ‘brute force’ approach like deduplication, NexGen applies a “phased process” data reduction technique. This starts by simple pattern matching that some space efficiency but with only a fraction of the performance impact of traditional deduplication. The next phase is to dedupe the data while it’s stored on solid state. In subsequent phases, deduplication is applied during migration and then finally as a post process, when the system in not busy. The combination of these four phases should provide the same or a greater level of efficiency than brute force duplication products use, but without the performance impact. This is because the last two phases are managed by the quality of service engine that was discussed earlier.

The final innovation in the NexGen storage system is that it provides enterprise class high availability and scaling. While HA and scaling are of course not new, providing them in a system with this level of performance and ease-of-use is unique.

The initial NexGen system called the n5 Storage System includes active-active storage processors for redundancy and performance, plus redundant disks, fans, and power supplies for complete availability. The system supports 48 GB of RAM, part of which is also used as a tier. Finally, it has 1.28 TB of PCIe solid state storage and 32 TB of 7200 RPM hard disk capacity. Connectivity to the attaching hosts can be via four 10Gb ethernet ports or sixteen 1Gb ethernet ports. The system communicates over standardized protocols and should be addressable from most major operating systems.

The user can also choose an additional 640 GB SSD PCIe board or the capacity option of another 32 TB of disk storage. It’s important to note that these are raw capacity numbers prior to any efficiencies provided by deduplication. In theory, in the right environment, like for example a virtual server infrastructure, a user may be able to get 5X efficiencies.

Storage Switzerland Take

NexGen’s storage system in some ways reminds me of the iPhone. None of the concepts and innovations described above are necessarily new. However, what is new is to have them integrated from scratch into a single package. Similar to the iPhone this makes features that were once difficult to access and hard to implement suddenly very easy to use and operate. In the future NexGen plans to add scale-out functionality to the storage systems but we’re pleased to see that initially customers can start with a single highly available unit and not have to deal with some of the complexity that scale-out storage systems bring.

NexGen Storage is a client of Storage Switzerland

Twelve years ago George Crump founded Storage Switzerland with one simple goal; to educate IT professionals about all aspects of data center storage. He is the primary contributor to Storage Switzerland and is a heavily sought after public speaker. With over 25 years of experience designing storage solutions for data centers across the US, he has seen the birth of such technologies as RAID, NAS and SAN, Virtualization, Cloud and Enterprise Flash. Prior to founding Storage Switzerland he was CTO at one of the nation's largest storage integrators where he was in charge of technology testing, integration and product selection.

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