Computational Storage:
99.999% Quality of Service (QoS) with NVMe systems


A service level agreement with 99.999 % availability for computational storage systems is considered a "magic value". That is only 5 minutes of downtime per year.

To achieve this, a new approach to data storage is required. A solution that maximises the read experience and write performance. Power consumption and scalability are also optimised in NGD's products.

In this regard, modern computing architectures have shown that the "fastest" is not always the best solution for maximising the performance of computing and storage infrastructures.

While the pure IOPS performance of storage continues to increase with the move from SATA/SAS to NVMe, as well as from PCIe Gen 3.0 to Gen 4.0, it has been shown that maximising the bandwidth of these interfaces does not necessarily lead to a more powerful system solution overall.

This is especially true for the platforms now available that can support 48 drives or more in a 2U enclosure. We have found that the performance data of the individual drives becomes irrelevant if the system-level interfaces are not able to aggregate that much raw bandwidth (BW). The drives get faster, but the system interface bandwidth is still limited - you simply cannot force more data down the line.

Asymptotic performance limit

Device-level speed limited by CPU power and/or network interfaces leads to an asymptotic performance limit, and this bottleneck comes at a high cost. A storage device with a higher interface bandwidth requires an expensive storage subsystem. This subsystem in turn requires a high performance controller with many channels, additional memory and increased dies.

Focus on latency as a solution

A new trend is emerging that addresses this very problem. Whether it is called performance optimisation or QoS (quality of service): The approach is to use storage such as NVMe drives that offer high internal read bandwidth with optimised write performance to maximise the use of many drives per system by customer applications. With this focus on latency, each storage device is able to respond to host requests in an extremely predictable manner.

This means 99.999% availability

A common measure of this consistency is measured by a number of "nines". For a storage device to achieve a value of 5x9, it must complete tasks within a given target window 99.999% of the time. This means that less than one in 10,000 commands may be completed outside of a time window, regardless of the activity in that device.

A computational example

An "analogous" way of looking at this is to model boarding an aircraft. It would be most efficient to board the aircraft from the rear, first at the window, then the middle, then the aisle, and then gradually move forward. In this way, a boarding process with an efficiency of 99.999%, or in other words 5 nines, could be achieved. However, since boarding is done by class and membership status, the result is a completely random process. In the process, efficiency falls below 1x9 of Quality of Service (QoS) - a measure of the quality of a service from the user's perspective.

Solution for QoS requirements of computer applications

NGD Systems has developed a solution with patented algorithms for Elastic FTL, Programmable ECC and data placement integrated into the controller architecture. The core of the platform manages the reads and writes and ensures that the clean-up operations have no negative impact on host QoS. A tighter distribution of response times indicates higher consistency.


The figure shows the 5-nines distribution for the NGD Systems Intelligent Storage Platform and that of a competitor solution with identical workloads. For this test, the drives were run against a FIO script (Linux test platform) with a customer workload that mimics their mixed read and write use case.

The result: optimised response time performance that is scalable across platforms and workloads. All in an NVMe drive that consumes only 12 watts of power.

What you need to know about NGD Systems

NGD Systems manufactures the world's most advanced computational storage drives (CSDs). Here, new levels of performance are achieved that are required by the next generation of data-intensive applications.

Would you like to learn more about computational storage? Then book our GLYN Talk now

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