Let's take a 100GB database as an example. Most likely not all of that 100GB database is going to be active at any one time. Typically there will be certain rows or records that will be "hot" - like a patient record for someone who just called into your customer service department, or an employee list your accounting department accesses once every 2 weeks for running payroll. When that data gets accessed, it needs to be served up quickly, at flash speeds, and since we are leveraging a hybrid model we need to promote only the data that is necessary to complete the business function.
A NetApp FAS array will accelerate that data to flash on demand, at the time of access, and only promote the 4k blocks necessary to service the request along with some other blocks that make up what we call a "readset". A readset is something NetApp uses to pre-fetch data that is also requested when the blocks we just picked up are promoted to flash. We have some interesting patents on this technology, see here, and they are much more effective than a standard read-ahead request which will simply pull surrounding blocks based on the locality of data.
By using such a granular block size we don't promote data that doesn't need to be there, and by that action, we don't force data that needs to be in cache out. If your block size is larger, say 64k, it doesn't seem that impactful since that is a small measurement of storage, but it is in fact 16 times larger than NetApp FAS, and that can lead to requiring vast quantities of flash in your performance tier.
Along with fast, intelligent, granular data promotion there is another key piece of technology NetApp employs that drives tremendous efficiency to the flash tier. This technology is primary storage deduplication. Sure, it's great for saving space on disks, but disks are abundant and cheap, and where you need to save space in a hybrid array is in flash.
Since we are dedup aware throughout the stack the deduplicated data blocks on disk remain deduplicated in flash. So maybe that customer service agent handling that important call is also running on a virtual desktop. Let's say you have a 100 seat call center, with each desktop image at 20GB, that means you would need 2TB of flash to handle a fully staffed shift at SSD levels of performance. NetApp on the other hand will dedup those down to the single unique image, and only promote the blocks that are now shared by those 100 systems. Accelerating the same workload with 99% less cache is one of the ways NetApp drives efficiency in hybrid storage systems. The video below diagrams the differing cache sizes, and how our dedup aware architecture is able to drive performance enhancements along with space savings on disk.