Enterprise SSDs, a more reliable option than mechanical hard drives?

If mechanical hard disks still occupy the top of the pavement in business, SSD could eventually reverse the trend, as observed by a recent study

While mechanical hard drives still store most of the data in business and have become surprisingly reliable and profitable, SSDs are nonetheless making a breakthrough with businesses. All thanks to the performance offered now offered in compact and energy-saving housings.

A study conducted jointly by researcher Bianca Schroeder and NetApp, a company specializing in the field of enterprise storage, also takes stock of the reliability of these SSDs in companies.

If studies have been conducted on the reliability of SSDs in cloud data centers, their results are not applicable elsewhere. Cloud providers generally don't use standard SSDs - when you buy 100,000 at a time, providers give you what you want - nor do they use common RAID protocols in hardware business. And the SSDs they use are found in system architectures that include optimizations not available to matrix vendors.

A large-scale test

The study presented here covers nearly 1.4 million readers from three different manufacturers, 18 different models, 12 different capacities and four flash technologies (SLC, cMLC, eMLC and 3D-TLC). Rich data, provided by NetApp automated telemetry, includes disk replacements (including reasons for replacements), bad blocks, usage, disk age, firmware versions, and the role of the disk (for example, data, parity or reserve).

Surprise: readers with LESS usage experience higher replacement rates. In addition, breakage cases increase during the first year of field use before starting to decrease.

Another observation: the most expensive SLC (single level cell) disks are NOT more reliable than MLC disks. And if the new high-density 3D-TLC (three-level cell) players have the highest overall replacement rate, the difference is probably not due to 3D-TLC technology, but to the capacity level or size of cells used in the player. High density cells have more failures.

Not all SSDs are created equal

This study also highlights the following observations:

• Not all SSDs offer the same reliability. Annual replacement rates range from 0.07% to almost 1.2%, with an average TRA of 0.22% for the entire population.
• Even for disc models from the same manufacturer, with the same flash technology, the same age and a similar capacity, the TRA can vary considerably, from 0.53% for a 15 TB disc against 1.13% for its companion stable 15.3 TB.
• Even after several years, the average replacement block consumed is less than 15%. Even discs with 99.9% of the spare blocks consumed consumed only 33% of their spare blocks.

The best news, which was the biggest concern when SSDs were released ten years ago, is that rapid wear is not an issue. Even after 2 or 3 years, less than 2% of the nominal life is consumed on average. Even hard drives in the 99.9th percentile consumed only 33% of their nominal life.