A read-intensive SSD is able to use NAND flash memory with a lower endurance level than an SSD that targets write-intensive workloads, such as online transaction processing, high-performance computing, and data warehousing. High numbers of writes can cause NAND flash wear-out, and manufacturers of SSDs intended for write-intensive workloads generally use more reliable types of NAND, overprovision the flash and/or use special algorithms to improve endurance.
Drive manufacturers sometimes offer SSDs of varying endurance levels and capacities earmarked for read-intensive, write-intensive or mixed workloads. For example, a read-intensive SSD might guarantee only one to three drive writes per day (DWPD) but offer higher capacity than a write-intensive SSD that supports up to 25 DWPD. The write-intensive SSD’s usable capacity may be lower because a greater percentage of NAND flash is reserved to handle garbage collection and compensate for potential chip wear-out or failure.
Read-intensive SSDs tend to use the least expensive types of NAND flash memory, such as multilevel cell (MLC) and triple-level cell (TLC) flash. Write-intensive SSDs more commonly use enterprise MLC (eMLC) or single-level cell (SLC) flash, which offer higher endurance than MLC and TLC. Storage systems that use less expensive MLC for write-intensive workloads generally employ special algorithms and other techniques to manage endurance.