3.10.1 About F20 PCIe Energy Storage Modules

The Sun Flash Accelerator F20 PCIe card includes an energy storage module (ESM) to ensure data integrity during a power interruption, functioning similar to a battery backup.

Sun Flash Accelerator F20 PCIe cards accelerate performance in Oracle Exadata Rack by caching frequently-accessed Oracle Database data and avoids the need to do physical I/O to the disk in Exadata Storage Server. Write operations to the flash cards are temporarily staged in volatile local DRAM memory on the card to speed write operations. The data in the DRAM is protected by an Energy Storage Module (ESM) which provides enough electrical power, in the event of a power failure, to move the data in the DRAM to the local flash.

The flash modules used in Oracle Exadata X3 systems have an expected endurance of 10 years or more, even in write intensive applications. Flash endurance is determined primarily by the total data written to flash across many years, as well as the type of data written. No application runs at maximum flash write IOPS for every second of every day for years. Applications also do many reads and have periods of high and low activity, such as day versus night, quarter close, end of a trading day, and so on. A very highly write intensive application might average 25 percent of the maximum flash write IOPS when measured over many months. Each Exadata X3 storage server has a total flash write endurance of over 50 PB for typical database data. In a full rack, if the application writes an average of 250,000 8K flash IOPS (25 percent of maximum writes) for 10 years, then it will write a total of 41 PB of data to each cell. This is less than the 50 PB per cell endurance.

If the ESM does not have sufficient charge, then the F20 PCIe card operates in fail-safe write-through mode, bypassing the DRAM memory and writing all data directly to flash. This results in reduced write performance, but there is no data loss. Exadata Storage Server generates an alert when the ESM capacity is insufficient, and the ESM should be replaced.

The charge capacity of the ESM degrades over time, and its life expectancy is inversely proportional to the operating temperature. The worst case life expectancy of the ESM in Oracle Exadata Rack is as follows:

Type of Exadata Storage Server	Lifetime
Exadata Storage Server with Sun Fire X4275 Servers	3 years
Exadata Storage Server with Sun Fire X4270 M2 Servers	4 years