*3.2. Basic Primitives*

There are three primitive operations in DHRD, read, write, and initialization. Figure 3 shows these primitive operations of DHRD. Each primitive operation acts as follows:


Data can be completely restored from the SSD despite a power failure because the SSD always keeps up-to-date data. The data recovery efficiency of the DHRD depends on the mounted file system. The read performance is determined by the RAM, but the write performance has a bottleneck in the SSD. Consequently, the DHRD is applicable to a server that requires high durability and higher read performance than write performance.

**Figure 3.** The three primitive operations of the durable hybrid RAM disk; read, write and initialization.
