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In today's fast-growing data centers, enterprise IT managers are seeking to leverage high-performance solid-state drives (SSDs) to help accelerate access to data. New SSDs are now available with cost-effective, higher density MLC NAND flash memory — eliminating a key cost barrier to deployment. However, usage of MLC flash-based SSDs is plagued with inherent endurance and performance limitations of the flash media itself — especially if consumer-grade MLC SSDs are used in enterprise applications.
The reliability, availability, and serviceability needs of an enterprise SSD are ultimately determined by the SSD controller. STEC's SSD controller architecture with integrated CellCare™ Technology provides enterprise-class endurance and improved performance of MLC media using advanced signal processing and adaptive flash management algorithms. The option to incorporate MLC-based SSDs into enterprise |
infrastructure, in addition to SLC solutions, data center operators have the ability to choose the best solution to support their data center applications. The flexibility afforded to these operators by having enterprise-viable MLC alternatives will help proliferate their use in robust enterprise environments to eliminate data bottlenecks and improve the overall storage infrastructure.
STEC's SSD controllers with integrated CellCare Technology provide a higher-level of enterprise endurance while improving performance/price of the drive using advanced signal processing and adaptive flash management algorithms.
To effectively improve MLC SSD endurance, advanced media management techniques need to be implemented within the SSD controller (and managed internal to the NAND flash memory). Using digital signal processing (DSP) functionality, the SSD controller can support complex management technologies such as dynamically adjusting the program and erase charges to achieve higher levels of efficiency. This enables algorithms to not only monitor how cells are being used but also predicts how reads and writes will affect performance over the long term. In this way, the algorithm can spread out cell wear to ensure consistent performance over time.
Extending the life of NAND flash memory in an SSD requires a flexible and intelligent controller architecture that can analyze and adapt dynamically to the changing characteristics of the flash cells as they age. Unmanaged MLC-based SSDs are not suitable for the continuous duty cycles and heavy workloads required for today's demanding network environments. Through the use of SSDs built with adaptive flash managementalgorithms and advanced signal processing techniques, IT professionals |
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can confidently accelerate network access with near-zero downtime and advanced data protection at the lowest cost per I/O. By extending the useful life of an enterprise MLC flash-based SSD delivers a higher return on the SSD investment.
The challenge with Flash Memory is that it wears out when you write to it. In an Enterprise environment with mission critical data, a continuous duty cycle demands Flash SSDs are challenged with meeting the endurance demands of a busy datacenter. CellCare is a proven set of technologies that actively manages flash memory from inside the chip by using custom controllers and firmware to increase the lifecycles of the flash calls over the working life of the SSDs.
How well a controller manages the flash memory determines whether the SSD can be used in enterprise applications that require 24/7/365 uninterrupted operations under heavy read and write workloads. STEC's CellCare Technology is designed for this specific purpose, making it the key ingredient for MLC flash-based, enterprise-class SSDs and provides three definitive benefits:
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Improved endurance of MLC media; |
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Enhanced performance of MLC media; and |
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Reduced media access error rates and consistent performance over the useful life of the drive. |
| CellCare Technology improves SSD endurance through the use of adaptive flash management algorithms. By proactively managing data cells throughout the life of the SSD provides improved reliability and reduced bit error rates. In addition, CellCare Technology employs advanced signal processing techniques to dynamically manage flash wear which eliminates the need for read-retries by accessing error-free data, even at vendor-specified endurance limits. CellCare Technology also employs techniques such as predictive read-optimization that ensures there is no loss of performance during the useful life of the drive. |
Incorporating controller-based media access management, CellCare Technology dynamically adjusts over the lifetime of the media to reduce the Uncorrectable Bit Error Rate (UBER) and advanced ECC techniques enable a higher degree of protection against media errors, leading to improved endurance of MLC flash media while maintaining high performance over the useful life of the drive.
CellCare Technology fills the gap between eMLC and SLC flash by not only improving endurance, but performance and reliability as well. As a result, STEC MLC flash-based SSDs with CellCare Technology warrant 30 full capacity writes per day for five years on the ZeusIOPS XE SSDs. Because SSDs can slow down and degrade due to the increased use of error correcting codes and retries required to overcome read issues (the more retries required, the slower the performance over the life of the drive). CellCare Technology enabled MLC SSDs deliver fewer errors and retries reducing drive degradation while extending its useful life.
What makes CellCare Technology possible is STEC's proprietary, highly advanced SSD controller that transforms the raw, generic flash into an enterprise-class SSD. Since all flash is not created equal, it's STEC's SSD controller that dynamically measures and manages flash media wear to extend its life without sacrificing performance. It uses advanced signal processing functions to improve flash endurance, adaptive flash management algorithms to actively manage NAND wear, and media error management and tuning functions that adjust over time and the life of the media.
To understand the benefits of CellCare Technology, it is important to understand the different types of flash memory available. The three types of NAND flash memory include SLC, MLC and 'enhanced' MLC (eMLC). The main difference between SLC and MLC/eMLC is the number of bits stored per NAND cell. SLC stores 1-bit of data per cell, while MLC and eMLC store 2 bits. The main difference between these flash memory types is captured in the table below.
| $/GB |
$$$ |
$ |
$+ |
$ |
| Endurance (cycles) |
100K |
3-5K |
30K |
60K |
| ECC |
8b/512B |
18b/512B |
18b/512B |
32b/512B |
SLC NAND flash typically supports more than 100,000 write cycles per cell and provides a very reliable and useful life of 10 to 20 years, making it the flash technology of choice for enterprise applications. MLC flash memory is less reliable and withstands no more than 3,000 write cycles per cell in 3x nanometer process geometries. The limited write endurance of MLC flash makes it well-suited in its unmanaged state for consumer applications, where the media is used primarily for reads.
To attain marginally higher endurance, eMLC flash memory uses a die-screening process of consumer MLC flash or a static tweaking process of flash process parameters, such as increasing write time (to slow down the wear-out characteristics) and program time. The result is higher endurance, but with slower performance, rendering eMLC flash unsuitable for true enterprise-class applications.
At present, neither MLC nor eMLC flash meet the endurance requirements of 10 full drive capacity writes-per-day, and as process geometries shrink, the endurance and retention capabilities will significantly decrease as well. Additionally, the write performance of MLC flash is 30% to 40% slower than SLC flash media, and eMLC flash performance is 20% slower than MLC flash. Both MLC and eMLC flash require higher error correction code (ECC) capabilities to match those of SLC flash.
Additionally, the bit error rate (BER) of eMLC and MLC flash increases during the useful life of the product which makes the components more prone to failure as they age. The read performance of eMLC flash deteriorates during the life of the product, which makes eMLC flash unsuitable for ever-intensive enterprise deployments that demand consistent SSD performance. eMLC flash bridges endurance gaps at the expense of slower performance, since multiple read retries are required due to increased bit errors that occur over the life of the media.
CellCare Technology improves the endurance of MLC flash at the cell level inside the NAND to achieve the heavy duty cycles of enterprise applications without sacrificing performance.
Unlike traditional MLC flash-based SSDs, and even SSDs using eMLC, STEC's MLC SSDs based on CellCare Technology are engineered to meet the demands of the enterprise: 1) the performance and endurance you expect from SLC flash-based SSDs; 2) the capacity and low cost per IO advantages of SSDs based on MLC flash.
No-compromise performance, proven endurance and lower cost add up to the world's first and most widely deployed enterprise-class MLC-based SSDs. With STEC CellCare Technology, the industry will be able to deploy an expanding array of differentiated, cost-effective MLC SSD products. And data center managers can trust SSDs built with CellCare Technology to deliver consistent performance and the endurance required for robust data center applications.
For example, STEC's ZeusIOPS® XE SSD with CellCare Technology allows the drive to exceed industry endurance standards. It is designed to deliver at least 30 full capacity writes per day for five years. That is the equivalent of 33 Petabytes of data on a 600 Gigabyte drive over its lifespan. That adds up to lower total cost of ownership (TCO) in an enterprise data center.
With patented CellCare Technology, STEC is meeting the growing demands of enterprise networks and connected applications to Accelerate Access to Data™. CellCare Technology is designed to help minimize total cost of ownership™ and maximize return on investment-throughout the enterprise.
*Full capacity writer per day for 5-years
