SSD technology brings an unprecedented level of storage I/O performance to modern storage systems. With that improved performance comes a premium price. The goal with SSD should be to use as little of it as you need, make sure that what you have is near capacity AND it only contains the most active data. That is a tall order for today's busy storage manager and this is where 3PAR's Autonomic Storage Tiering helps alleviate the problem by automatically moving data to the correct tier of storage at the correct time. 

What makes 3PAR unique thus far is that they are the first to bring sub-volume tiering to an enterprise class system. While other systems need to migrate entire LUNs, 3PAR can migrate specific chunks of files or volumes. They can also apply different thresholds based on the application through a feature known as QOS gradients. QOS gradients bias on the data movement based upon a performance, balanced or cost setting. This setting accelerates or decelerates data movement toward a particular class of resources and is particularly useful when differentiated levels of service need to be applied to an application for a particular time period – month end for example. This type of quality of service is critical. Activity of the file alone does not mean that it should be on SSD. SSD should be reserved for applications, servers and users that can take advantage of the performance boost. 

3PAR's new system leverages something called I/O Rate Density as the key component in data movement. This is a calculation of the I/O per GB per minute. This allows the 3PAR system to identify active and inactive regions and then move them to the correct tier of storage. All of this migration is done non-disruptively over the application life-cycle. The important fact is that 3PAR has been working with sub-volume data handling for years. This is not a revolutionary capability for their system but a safe, evolutionary next step. 

The 3PAR architecture is also ideal for SSD. With other systems we have seen that the SSD will actually saturate the shelves of the system or the storage controller itself. 3PAR's parallel, cluster system, again in place for years, is almost tailor made for the high performance that SSD's deliver. IOPS are evenly spread across all the nodes in the cluster, with up to eight nodes available for handling I/O processing.

For the SSD mechanism itself 3PAR chose the SLC based STEC Mach 8 IOPS. This is a different approach than the more expensive but greater capacity Zeus IOPS. Essentially you get twice the number of drives at the same total capacity for a little more money. More drives of course yields better performance and more cost effective sparing. Interestingly, thanks to the 3PAR clustered architecture, you can mix the SSD drives in the same chassis as Fibre or SATA drives. 

3PAR's combination of automated tiering with mid-ranged SSD and their high performance scalable architecture is very compelling. They address many of the concerns that I have had as traditional storage vendors enter the once niche SSD market.

George Crump, Senior Analyst

- Autonomic Storage Tiering

Disclosure: 3PAR is a client of Storage Switzerland.

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