Cache Flash Memory; Cfm Operation; Cache Flash Memory Capacity - Hitachi G1000 Hardware Manual

Cache flash memory

The cache flash memory (CFM) is contained in the cache backup modules in
the controller, along with the cache backup batteries. Like the cache memory,
a CFM feature consists of a pair for redundancy purposes. They provide
backup for the cache in case of power or component failure. The following
figure shows two CPAs (2-3, and 1-4).

CFM operation

Each CFM blade connects directly to its corresponding CPA blade and backs
up the data in that CPA blade if power fails. When data that is not stored on
disk is written to the cache, it is written to one blade of the CPA and mirrored
to the other. If one CFM fails, or one phase of the power fails, the other CFM
backs up the mirrored data from its corresponding CPA blade, and no data is
lost. In the unlikely event where a CFM has failed and a full power failure
occurs, the other CFM backs up the mirrored data from the CPA without any
loss of data.

Cache flash memory capacity

The recommended size of the installed cache flash memory depends on the
size of the cache memory, and is automatically selected when defining the
configuration for the system.
The following table shows CFM capacities per controller with both small and
large cache memory backup assemblies.
1
2
48
Hitachi Virtual Storage Platform G1000, G1500, and Virtual Storage Platform F1500 Hardware Guide
Number of controllers
1 CFM
2 boxes /SSDs
2 CFMs
4 boxes /SSDs
1 CFM
2 boxes /SSDs
2 CFMs
Number of CFM
features (pairs of Memory module size
boxes)
128 GB
256 GB
128 GB
256 GB
128 GB
256 GB
128 GB
Introduction
1
CFM size
256 GB
512 GB
512 GB
1 TB
512 GB
1 TB
1 TB