An ongoing concern about flash storage is its endurance. In other words, IT professionals are concerned that these systems will wear out due to heavy write activity prior to being fully amortized. All-flash arrays may be an exception. These systems tend to benefit from the reality that only 10% or so of data is active at any given point in time in a data center. As a result, the wear on these systems is well below average. It is so low that over a year ago Storage Switzerland suggested that TLC / 3D NAND would be appropriate for all-flash arrays.
Making TLC Enterprise Safe
Triple Level Cell (TLC) NAND and 3D NAND use different techniques to pack more bits into the same space. Greater density means a lower cost per unit and in flash storage reducing cost is critical to broader adoption.
The concern with TLC/3D NAND has been durability. More bits per cell means that cell should wear out faster but again in the all-flash array use case this may be a non-issue if that TLC layer is properly used and protected. The simplest way to hide this vulnerability is to front end it with a small but more reliable SLC or MLC tier that acts as a shock absorber.
Dell Introduces Mainstream Read-intensive Drives
Dell was one of the first companies to leverage mixed flash types in their storage systems. In September of 2013 Storage Switzerland published our lab report Mixed All-Flash Array Delivers Safer High Performance that details Dell’s technology, that at the time used SLC and MLC. Today Dell announced that its flash arrays would now have three flash drive options; Write-intensive (SLC), Premium Read-intensive (MLC) and Mainstream Read-intensive (TLC).
A combination of flash drives can be used to configure a Dell SC series. That combination will change based on use case. The system leverages Dell’s data progression technology to move the data between the types of flash drives automatically. For most data centers, a small SLC tier, and a large TLC tier will be ideal. In this configuration data is initially stored on the SLC tier, then as it becomes less active moved to the TLC tier. It can also transfer data to a third hard disk drive based tier if the customer chooses.
All-Flash arrays, for the most part, provide limited choice in media. Dell offers three options, four if an HDD tier is considered.
Do We Need Dedupe Anymore?
Most all-flash arrays today use some form of MLC based flash. They then add deduplication and compression to reduce further costs. Without proper design, data efficiency can impact performance. It can also make determining the exact value difficult. The actual storage savings that deduplication delivers is never actually known until after the storage system is installed and running. The variable cost is a result of the return on data efficiency being different for every environment.
Dell avoids the unknowns of potential performance impact and storage cost by delivering an all-flash array the meets an aggressive price point with native storage capacities. If the storage system provides thin provisioning and writeable snapshots combined with competitive raw capacity price points, one has to wonder if deduplication and compression are now past their prime. At a minimum deduplication technology needs to up its game.
Dell’s announcement is ideally suited to the data tiering that has been a part of their SC series offering for years. They also made improvements to make the storage system more flash ready, like making movement between tiers happen more frequently. The addition of TLC as a supported tier of storage allows Dell to leverage the strength of the SC storage software and offer a very compelling price point for its users.