Glossary

E

energy storage module (ESM)

Device containing supercapaciters that provides enough backup power to enable data in volatile memory to be written to non-volatile flash.

A functional ESM is critical for maintaining FMod performance. In the event of an ESM failure, the FMod reverts to a write-through(non-cache) mode to ensure data integrity, at the expense of write performance.

F

flash memory

One of two types of solid-state memory on an FMod.

Flash memory provides persistent data storage on the FMod.

flash module (FMod)

A storage device containing solid-state memory.

The FMod consists of two logical components: volatile storage and flash memory. While volatile storage provides read/write performance similar to RAM, data integrity is potentially at risk during an electrical power interruption. The energy storage module (ESM) is necessary to preserve data integrity and protect the hardware during a sudden power loss.

The system treats each FMod as a separate storage volume. FMods are managed using the same tools as those for conventional (platter-based) hard drives. An FMod can be configurated as a boot device.

The Sun Flash Accelerator F20 PCIe card contains four FMods.

V

volatile storage

One of two types of solid-state memory on an FMod.

Volatile storage provides read/write performance similar to DRAM. Data is regularly written to flash memory (as a background task in a first-in-first-out manner) using a write-through mode.

W

write-back mode

High-performance data access mode in which data is written to and read from volatile storage.

Write-back mode is available only when the ESM is properly charged and online.

write-through mode

Persistant data access mode in which data is written directly to flash memory by-passing the DRAM.

The Sun Flash Accelerator F20 PCIe card reverts to write-through mode if it detects a failure with the ESM, or if the ESM is charging. This ensures data integrity, at the expense of write performance.