In the past year, we’ve seen flash storage expand into areas where it wasn’t commonly used before. Thanks to the introduction of denser, more affordable quad-level cell (QLC) flash storage, it’s now moving into markets previously occupied by nearline solutions.
The cost of flash per gigabyte has dipped close to that of traditional hard disk drives (HDDs), then jumped back up as manufacturers aimed for profitability. Many advocates of flash storage are convinced that hard drives will soon become obsolete, predicting a shift towards all-flash data centers.
Now, let’s break down what enterprise flash storage really means. It consists of systems with several flash drives all packed into a rack-mounted array in data centers. These storage arrays aggregate the capacity of multiple drives, managed by controller hardware that oversees everything from input/output (I/O) tasks to essential maintenance activities like wear leveling and garbage collection. Overall, enterprise flash storage can range from tens of terabytes to petabytes.
What about QLC? This newer flash storage type allows each chip cell to hold four bits of data, using 16 states. This increases storage density and drops costs compared to previous technologies like TLC, SLC, and MLC. Right now, many enterprises still rely on TLC drives for essential applications, but QLC is gaining ground, especially for unstructured data. As more states are packed into each cell, storage becomes denser, but this can lead to potential endurance issues.
Next up is NVMe, a protocol designed for flash storage use. Before NVMe, flash drives relied on older interfaces like SATA and SAS, which weren’t tailored for the speed of flash. NVMe optimizes data queues and buffers, boosting performance significantly. Suppliers are now also developing ways to use NVMe over various fabrics, extending connectivity options across data centers.
Let’s talk about HDDs. These magnetic devices, with spinning disks, have been around for decades and were the dominant storage type long before flash came on the scene. They can also be assembled into rack-mounted arrays like flash storage, but flash technology has clearly outpaced them in speed.
When it comes to performance, flash drives are distinctly faster than HDDs. With access times in the low milliseconds or even microseconds, flash can handle many more input/output operations per second (IOPS) than HDDs, which typically operate in the multi-millisecond range. In throughput, flash offers rates several times faster than HDDs due to the absence of moving parts, while HDD capacities can max out around 22TB, with flash drives marketed up to 60TB.
Now, about costs: right now, flash is generally more expensive per gigabyte than spinning disks. Prices for flash surged in late 2023 as manufacturers restricted production, but they have since declined. In October 2023, HDD averaged about $0.05/GB for SAS and $0.035/GB for SATA drives, while flash went for about $0.075/GB. By September 2024, HDD prices stayed stable, yet flash prices had dropped slightly to around $0.085/GB.
Will flash really replace HDDs? Some companies, like Pure Storage, predict that by 2028, HDDs will be obsolete, claiming their flash products can provide significantly more storage capacity. However, other companies, such as Panasas, highlight that many hyperscale data centers still rely heavily on HDDs, often at a 90:10 ratio favoring disks.
In the cloud, both flash and HDD options are available to enterprise customers. Often, the choice hinges on performance needs and cost, making it possible for cloud users to select either type without knowing the underlying technology. Major cloud providers like AWS, Microsoft Azure, and Google Cloud Platform all offer solid-state options tailored to different performance and capacity requirements.
The concept of an all-flash data center has circulated for a decade, promising to replace HDD storage entirely. Supporters argue that as flash storage costs continue to decline, the advantages of fast data access become even more compelling, especially for data-intensive tasks. For example, modern analytics and quick recoveries from attacks are cited as benefits of moving to flash.
While advocates push for an all-flash future, others note the persistence of spinning disks, particularly for certain datasets. According to HDD producers, around 85% of data remains on spinning disks, pointing out that a rapid transformation isn’t on the horizon due to current capacity limitations in flash technology.