There are different types of SSD available today. These range from customer-oriented devices using the Multi-Level Cell (MLC) technology through to Enterprise Multi-Level Cells (eMLCs)  and enterprise Single-Level Cell (SLC) chips. The critical difference is the durability of the chips and the device itself. You should never use customer SSDs in your infrastructure because they are not intended to run continuous workloads at all.

The endurance of SSDs is often defined as the amount of Drive Writes Per Day (DWPD). The DWPD number will show you how often you can rewrite the whole SSD every single day within the warranty of the SSD. If you continuously go over this number, the chip cells will not be able to handle the load, and errors start to appear until the whole device is completely unusable.

Today, manufacturers have introduced several SSD types based on their designated use:

• Write intensive SSDs: These devices are usually equipped with SLC chips and they have a high DWDP, usually around 10, meaning that you can rewrite them ten times every single day. Write-intensive SSDs are commonly used as a caching tier, so the data is always written to these devices and altered during the destaging process to lower performing devices. The capacity is usually up to 1 TB (±800 GB).
• Read-intensive SSDs: The DWDP of these devices is much lower than write-intensive SSDs, usually under 1, meaning that you should not rewrite the whole capacity within a single day. They have a much higher capacity than write-intensive SSDs (3.84 TB for SATA3 devices), and they are also cheaper. They do not use SLC chips but eMLC chips instead. The primary use case for this kind of device is the capacity tier.

• Mixed-use SSDs: This is a compromise between WI and RI devices. They have a higher DWDP then RI SSDs but a lower DWDP than WI devices (usually between 2 and 5). Their capacity and price are also in between RI and WI devices. They are often used as a single, all-purpose device. If you do not want to create multiple storage tiers, mixed-use SSDs are the way to go.