Using ioControl software, applications can be assigned an IOPS level; a business intelligence app is given 25,000 for example. They can also be assigned a throughput value. Like IOPS the number is treated as a target minimum, with the system software ensuring that they never get less than this minimum.
They can also be assigned a latency which is treated as a target maximum, with data access latency never exceeding this maximum value.
There are five performance policies available and these are linked to the IOPS, throughput and latency service levels.
The policies are: mission critical, business critical, (not so) business critical, non-critical, and (even less) non-critical. These policies have declining numbers of IOPS, throughput in MB/sec, and latency in milliseconds associated with them. Throughput, latency and IOPS will be sacrificed for non-mission critical apps (volumes) to maintain the more important mission critical app’s performance.
Mission critical volumes will read cache data into flash more quickly than Business Critical volumes. So-called Dynamic Data Path algorithms in the Prioritised Active Flash subsystem keep an app's 2-10 per cent active data in flash. The algorithms work in conjunction with the QoS engine to meet the set per-volume priorities.
QoS performance policies are applied to storage volumes and can be changed on the fly by sysadmins. The performance policy values themselves can also be changed, and performance against the policies can be monitored using a dashboard GUI.
NexGen claims its "prioritized Active Cache allows 2.5x more data in flash versus hybrids and reduces flash capacity required by 10x versus all flash arrays".
The company provided a canned quote from a customer, namely Michael Frank, manager of the IT services group at NCS, a financial services company, who said: "With NexGen, we’re able to assign specific priorities to each application, change them in real time, move a particular data set up into a higher service level for a few days when it’s critical to the business, and then move it back down when that task is complete."
He sums up the capabilities nicely enough. Give the man a discount on his support contract.
Read more about this QoS stuff in a Nexgen architecture white paper.
Critical success factors
Why can NexGen succeed against the weight of hybrid mainstream and startup competition? It's pitch is that it will deliver a better quality of storage service to applications than any competing system because it uses more and faster flash, and has an app-aware storage performance profile capability. A ground-up-designed operating system underlies this.
Much will depend on price/performance and support, an area where Nimble is especially strong. NexGen also has to overcome the challenge of VM-focussed storage management from Tintri but VMware has in a way provided a platform for that possibility with its VVOLs concept.
NexGen's software already has some VMware integration via a vSphere plug-in and VAAI to ensure plug and play deployment.
NexGen's N5 hybrid flash array products are available now with pricing starting from $55,000. ®