As data centers push for higher data throughput and reduced latency, many are transitioning from hard disk drives (HDDs) in their servers to solid-state drives. This shift aims to boost performance, increase efficiency and cut operating costs. But not all SSDs are built the same, making it key to select the right type for enterprise and other environments.
SSD classes are distinguished by the two main components: the flash storage controller and the non-volatile NAND flash memory used to store data.
In today’s market, SSD and NAND flash memory consumption are split into three main groups:
- Consumer devices (tablets, cameras, mobile phones)
- Client systems (found in personal computers such as notebooks, desktop computers, and Ultrabooks)
- Enterprise computing platforms (HPC, data center servers)
Choosing the right SSD for enterprise use involves more than simply replacing HDDs. SSDs come in various form factors (such as 2.5″) and interfaces including Serial ATA (SATA), Serial Attached SCSI (SAS) and the newer NVMe PCIe which directly connects storage to the server’s CPU.
Despite their ease of deployment, not every SSD is suitable in the long term for enterprise workloads, and the cost of making the wrong – or cheapest – choice can lead to premature wear, inconsistent write performance and increased latency.
To guide the selection process, let’s explore the three key characteristic that separate enterprise-grade SSDs from their client-class counterparts: performance, reliability and endurance.
Regional Director for UK & Ireland and DRAM Business Manager for the EMEA Region at Kingston Technology.
1. Performance
Enterprise SSDs are designed to provide sustained high-speed read and write operations for both sequential and random data requests from the CPU through multi-channel architecture and parallel access from the SSD’s controller to the NAND flash chips.
In environments handling complex workloads like real-time data analysis, CAD collaborations or global banking transactions, the storage devices must deliver low latency and simultaneous multi-client data access without any degradation in response time. User productivity is a direct result of low latency.
Client applications involve only single users or application access with a higher tolerable delta between the minimum and maximum response time (or latency) on any user or system actions.
SSDs used in complex storage arrays, such as Network Attached Storage, Direct Attached Storage or Storage Area Network can also be negatively impacted by mismatched performance, causing problems with the storage array latency, the ability to sustain performance and, of course, quality of service as perceived by users.
Unlike client SSDs, enterprise SSDs use multi-channel architectures and parallel NAND access to maintain peak and steady-state performance, ensuring consistent quality of service (QoS) even during traffic surges.
2. Reliability
NAND flash memory, though fast, comes with inherent limitations such as finite life expectancy (as NAND flash cells wear during repeated writes) and natural error rates. Enterprise SSDs combat this with advanced Error Correction Code (ECC) mechanisms to manage bit errors and maintain data integrity.
The SSD controller’s ability to correct bit errors can be interpreted by the Uncorrectable Bit Error Ratio (UBER), “a metric for data corruption rate equal to the number of data errors per bit read after applying any specified error-correction method”, as defined by the industry standards association, JEDEC. Enterprise class SSDs differ from client-class SSDs in terms of their ability to support heavier write workloads, more extreme environmental conditions and to recover from a higher Bit Error Ratio than a client SSD.
To further enhance reliability, enterprise SSDs often integrate end-to-end data protection. This ensures data accuracy as it moves between the host and NAND storage, using parity data and redundancy checks to recover corrupted data blocks. In these SSDs, periodic checkpoint creation, cyclic redundancy check (CRC) and ECC error correction are also implemented in an end-to-end internal protection scheme to ensure the integrity of data from the host through the flash and back to the host.
SSDs can incorporate physical circuitry for power loss detection that manages power storage capacitors on the SSDs. This allows the capacitor to complete pending writes during sudden outages, adding another layer of security. Power loss protection (PLP) circuitry is usually required for applications where data loss is not recoverable.
There are environments in which the use of software-defined storage or server clustering can cut the need for hardware-based power fail support as any data is replicated onto a separate and independent storage device on a different server or servers. Web-scale data centers often dispense with power fail support using software defined storage to RAID servers to store redundant copies of the same data.
3. Endurance
Endurance reflects how long an SSD can reliably handle data writes. NAND Flash cells degrade with each program or erase (P/E) cycle until they are unable to store data accurately. When this happens, the degraded block is removed from the user addressable storage pool and the logical block address (or LBA) is moved to a new physical address on the NAND Flash storage array.
A new storage block is used to replace the bad one on the SSD. This also means that the Bit Error Ratio rises, resulting in a set of management techniques being implemented on the enterprise SSD controller to manage the cell capability to reliably store data over the expected life of the SSD.
Enterprise SSDs are built for continuous 24/7 use, unlike client SSDs that typically operate on an 8-hour cycle, but in both cases their endurance needs to be understood. To measure this, manufacturers usually use the JEDEC committee endurance measurement metric of ‘terabytes written’ (TBW), which estimates the amount of data an SSD can handle before the NAND flash becomes unreliable.
The write amplification factor (WAF) – the ratio of actual NAND writes compared to data received from the host – also impacts endurance. Higher WAF can accelerate wear, so enterprise SSD controllers use sophisticated algorithms to manage data distribution and extend lifespan.
When considering other measures of component reliability, the ‘mean time between failure’ (MTBF) is an important model. Enterprise SSD components are assessed on longevity and their ability to manage the voltages across all NAND flash memory over their lifespan. All enterprise SSDs should be rated at least at two million hours MTBF.
SMART monitoring and reporting on enterprise-class SSDs allows the device to be assessed for life expectancy prior to failure based on the current write amplification factor (WAF) and wear level. Pre-failure predictive warnings for failure events, including loss of power, bit errors occurring from the physical interface or uneven wear distribution, are often also supported.
Client-class SSDs may only feature the minimum SMART output for monitoring the SSD during standard use or post failure.
Some SSDs also allow for an increased reserve capacity of NAND flash memory to be allocated as an over-provisioned (OP) spare capacity. Not visible to the user and operating system access, this is a temporary write buffer for higher sustained performance and as a replacement of defective flash memory cells and enhances the reliability and endurance of the SSD.
In summary
Understanding the differences between enterprise and client SSDs — from NAND endurance to performance optimization — is essential when upgrading data center storage. Enterprise SSDs offer robust solutions tailored for high-intensity workloads, ensuring reliability and minimizing downtime.
By carefully selecting SSDs suited to specific applications, organizations can future-proof their storage infrastructure and maintain seamless operations.
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