What is a computational storage drive? Much-needed help for CPUs

Maria J. Danford

The unavoidable slowing of Moore’s Regulation has pushed the computing sector to undertake a paradigm change from the traditional CPU-only homogeneous computing to heterogeneous computing. With this alter, CPUs are complemented by particular-reason, domain-particular computing materials. As we have seen about time, this is very well mirrored by the remarkable expansion of hybrid-CPU/GPU computing, significant investment decision on AI/ML processors, huge deployment of SmartNIC, and much more just lately, the emergence of computational storage drives.

Not incredibly, as a new entrant into the computing landscape, the computational storage generate appears really unfamiliar to most people and several concerns by natural means arise. What is a computational storage generate? The place ought to a computational storage generate be employed? What variety of computational functionality or functionality ought to a computational storage generate offer?

Resurgence of a straightforward and decades-outdated notion

The essence of computational storage is to empower facts storage devices with additional facts processing or computing capabilities. Loosely speaking, any facts storage system — crafted on any storage technological know-how, this sort of as flash memory and magnetic recording — that can have out any facts processing duties past its main facts storage responsibility can be called a computational storage generate.

The straightforward notion of empowering facts storage devices with additional computing functionality is definitely not new. It can be traced again to much more than twenty several years in the past as a result of the intelligent memory (IRAM) and intelligent disks (IDISKs) papers from Professor David Patterson’s group at UC Berkeley all-around 1997. Essentially, computational storage enhances host CPUs to variety a heterogeneous computing system. 

Computational storage even stems again to when early tutorial research confirmed that this sort of a heterogeneous computing system can significantly improve the overall performance or power efficiency for a selection of apps like databases, graph processing, and scientific computing. Nonetheless, the sector selected not to undertake this notion for serious globe apps basically for the reason that past storage professionals could  not justify the investment decision on this sort of a disruptive idea in the existence of the continual CPU improvement. As a result, this subject matter has become mostly dormant about the previous two decades. 

Fortunately, this notion just lately been given a significant resurgence of interest from both of those academia and sector. It is pushed by two grand industrial trends:

  1. There is a expanding consensus that heterogeneous computing should participate in an ever more essential job as the CMOS technological know-how scaling is slowing down.
  2. The significant development of significant-pace, good-point out facts storage systems pushes the technique bottleneck from facts storage to computing.

The idea of computational storage natively matches these two grand trends. Not incredibly, we have seen a resurgent interest on this subject matter about the previous number of several years, not only from academia but also, and arguably much more importantly, from the sector. Momentum in this place was highlighted when the NVMe conventional committee just lately commissioned a functioning group to prolong NVMe for supporting computational storage drives, and SNIA (Storage Networking Marketplace Affiliation) fashioned a functioning group on defining the programming product for computational storage drives. 

Computational storage in the serious globe

As facts facilities have become the cornerstone of fashionable data technological know-how infrastructure and are accountable for the storage and processing of at any time-exploding amounts of facts, they are plainly the greatest place for computational storage drives to commence the journey towards serious globe software. Nonetheless, the key question here is how computational storage drives can greatest provide the requirements of facts facilities.

Data facilities prioritize on price tag discounts, and their components TCO (complete price tag of possession) can only be diminished by means of two paths: less expensive components production, and greater components utilization. The gradual-down of technological know-how scaling has compelled facts facilities to ever more rely on the next route, which by natural means leads to the present trend towards compute and storage disaggregation. Despite the absence of the expression “computation” from their occupation description, storage nodes in disaggregated infrastructure can be accountable for a huge selection of hefty-responsibility computational duties:

  1. Storage-centric computation: Price tag discounts demand from customers the pervasive use of at-relaxation facts compression in storage nodes. Lossless facts compression is very well acknowledged for its significant CPU overhead, primarily for the reason that of the significant CPU cache miss out on level triggered by the randomness in compression facts flow. Meanwhile, storage nodes should make sure at-relaxation facts encryption as well. Furthermore, facts deduplication and RAID or erasure coding can also be on the process checklist of storage nodes. All of these storage-centric duties demand from customers a significant amount of computing ability.   
  2. Network-visitors-alleviating computation: Disaggregated infrastructure imposes a selection of software-stage computation duties on to storage nodes in purchase to drastically ease the stress on inter-node networks. In unique, compute nodes could off-load sure small-stage facts processing capabilities like projection, selection, filtering, and aggregation to storage nodes in purchase to mostly reduce the amount of facts that should be transferred again to compute nodes. 

To reduce storage node price tag, it is essential to off-load hefty computation masses from CPUs. Compared to off-loading computations to individual standalone PCIe accelerators for typical style follow, instantly migrating computation into every storage generate is a a lot much more scalable resolution. In addition, it minimizes facts visitors about memory/PCIe channels, and avoids facts computation and facts transfer hotspots. 

The will need for CPU off-loading by natural means calls for computational storage drives. Evidently, storage-centric computation duties (in unique compression and encryption) are the most effortless pickings, or small-hanging fruit, for computational storage drives. Their computation-intensive and set-functionality nature renders compression or encryption correctly suited for staying executed as tailored components engines inside computational storage drives. 

Relocating past storage-centric computation, computational storage drives could further more assist storage nodes to execute computation duties that intention to ease the inter-node network facts visitors. The computation duties in this category are software-dependent and as a result have to have a programmable computing cloth (e.g., ARM/RISC-V cores or even FPGA) inside computational storage drives.

It is clear that computation and storage inside computational storage drives should cohesively and seamlessly work collectively in purchase to offer the greatest attainable stop-to-stop computational storage support. In the existence of constant improvement of host-aspect PCIe and memory bandwidth, limited integration of computation and storage gets even much more essential for computational storage drives. For that reason, it is essential to combine computing cloth and storage media management cloth into a single chip. 

Architecting computational storage drives

At a glance, a commercially practical computational storage generate ought to have the architecture as illustrated in Determine 1 under. A single chip integrates flash memory management and computing materials that are linked by means of a significant-bandwidth on-chip bus, and the flash memory management cloth can provide flash entry requests from both of those the host and the computing cloth.

Offered the common at-relaxation compression and encryption in facts facilities, computational storage drives should personal compression and encryption in purchase to further more assist any software-stage computation duties. For that reason, computational storage drives should attempt to offer the greatest-in-class help of compression and encryption, preferably in both of those in-line and off-loaded modes, as illustrated in Determine 1.

computational storage drive ScaleFlux

Determine 1: Architecture of computational storage drives for facts facilities.

For the in-line compression/encryption, computational storage drives apply compression and encryption instantly along the storage IO route, staying transparent to the host. For every produce IO request, facts go as a result of the pipelined compression → encryption → produce-to-flash route for every read IO request, facts go as a result of the pipelined read-from-flash → decryption → decompression route. These kinds of in-line facts processing minimizes the latency overhead induced by compression/encryption, which is really desirable for latency-delicate apps this sort of as relational databases.

Furthermore, computational storage drives could combine additional compression and protection components engines to offer off-loading support as a result of very well-defined APIs. Safety engines could include things like a variety of modules this sort of as root-of-belief, random amount generator, and multi-mode private/community key ciphers. The embedded processors are accountable for assisting host CPUs on employing a variety of network-visitors-alleviating capabilities.

Eventually, it’s key to keep in mind that  a very good computational storage generate should very first be a very good storage system. Its IO overall performance should be at minimum equivalent to that of a regular storage generate. Without the need of a good foundation of storage, computation gets almost irrelevant and meaningless.

Subsequent the over intuitive reasoning and the by natural means derived architecture, ScaleFlux (a Silicon Valley startup corporation) has efficiently launched the world’s very first computational storage drives for facts facilities. Its solutions are staying deployed in hyperscale and webscale facts facilities throughout the world, aiding facts center operators to reduce the technique TCO in two means:

  1. Storage node price tag reduction: The CPU load reduction enabled by ScaleFlux’s computational storage drives makes it possible for storage nodes to reduce the CPU price tag. For that reason, without having modifying the compute/storage load on every storage node, a single can instantly deploy computational storage drives to reduce the for every-node CPU and storage price tag. 
  2. Storage node consolidation: One particular could leverage the CPU load reduction and intra-node facts visitors reduction to consolidate the workloads of many storage nodes into a single storage node. Meanwhile, the storage price tag reduction enabled by computational storage drives mostly improves the for every-generate storage density/capability, which further more supports storage node consolidation.

On the lookout into the potential

The unavoidable paradigm change towards heterogeneous and domain-particular computing opens a huge doorway for options and improvements. Natively echoing the wisdom of shifting computation closer to facts, computational storage drives are destined to become an indispensable element in potential computing infrastructure. Pushed by the sector-huge standardization endeavours (e.g., NVMe and SNIA), this emerging spot is staying actively pursued by much more and much more corporations. It will be thrilling to see how this new disruptive technological know-how progresses and evolves about the next number of several years.

Tong Zhang is co-founder and chief scientist at ScaleFlux.

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Copyright © 2021 IDG Communications, Inc.

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