6 Reasons SSDs Will Take Over the Data Center

The first samples of flash-based SSDs surfaced 12 years ago, but only now does the technology appear poised to supplant hard drives in the data center, at least for primary storage. Why has it taken so long? After all, flash drives are as much as 1,000x faster than hard-disk drives for random I/O.

Partly, it has been a misunderstanding that overlooks systems, and focuses instead on storage elements and CPUs. This led the industry to focus on cost per terabyte, while the real focus should have been the total cost of a solution with or without flash. Simply put, most systems are I/O bound and the use of flash inevitably means needing fewer systems for the same workload. This typically offsets the cost difference.

The turning point in the storage industry came with all-flash arrays: simple drop-in devices that instantly and dramatically boosted SAN performance. This has evolved into a model of two-tier storage with SSDs as the primary tier and a slower, but cheaper, secondary tier of HDDs

Applying the new flash model to servers provides much higher server performance, just as price points for SSDs are dropping below enterprise hard drive prices. With favorable economics and much better performance, SSDs are now the preferred choice for primary tier storage.

We are now seeing the rise of Non-Volatile Memory Express (NVMe), which aims to replace SAS and SATA as the primary storage interface. NVMe is a very fast, low-overhead protocol that can handle millions of IOPS, far more than its predecessors. In the last year, NVMe pricing has come close to SAS drive prices, making the solution even more attractive. This year, we'll see most server motherboards supporting NVMe ports, likely as SATA-Express, which also supports SATA drives.

NVMe is internal to servers, but a new NVMe over Fabrics (NVMe-oF) approach extends the NVMe protocol from a server out to arrays of NVMe drives and to all-flash and other storage appliances, complementing, among other things, the new hyper-converged infrastructure (HCI) model for cluster design.

The story isn’t all about performance, though. Vendors have promised to produce SSDs with 32 and 64TB capacity this year. That's far larger than the biggest HDD, which is currently just 16TB and stuck at a dead-end at least until HAMR is worked out.

The brutal reality, however, is that solid-state opens up form-factor options that hard disk drives can’t achieve. Large HDDs will need to be 3.5 in form-factor. We already have 32TB SSDs in a 2.5 inch size and new form-factors, such as M2.0 and the "ruler"(an elongated M2.0), which will allow for a lot of capacity in a small appliance. Intel and Samsung are talking petabyte- sized storage in 1U boxes.

The secondary storage market is slow and cheap, making for a stronger barrier to entry against SSDs. The rise of 3D NAND and new Quad-Level Cell (QLC) flash devices will close the price gap to a great extent, while the huge capacity per drive will offset the remaining price gap by reducing the number of appliances.

Solid-state drives have a secret weapon in the battle for the secondary tier. Deduplication and compression become feasible because of the extra bandwidth in the whole storage structure, effectively multiplying capacity by factors of 5X to 10X. This lowers the cost of QLC-flash solutions below HDDs in price-per-available terabyte.

In the end, perhaps in just three or four years flash and SSDs will take over the data center and kill hard drives off for all but the most conservative and stubborn users. On the next pages, I drill down into how SSDs will dominate data center storage.

(Image: Timofeev Vladimir/Shutterstock)