Hitachi F1500, Руководство по оборудованию

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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.
Number of controllers
Number of CFM
features (pairs of
boxes)
Memory module size CFM size
1
1 1 CFM
2 boxes /SSDs
128 GB 256 GB
256 GB 512 GB
2 CFMs
4 boxes /SSDs
128 GB 512 GB
256 GB 1 TB
2 1 CFM
2 boxes /SSDs
128 GB 512 GB
256 GB 1 TB
2 CFMs 128 GB 1 TB
48 Introduction
Hitachi Virtual Storage Platform G1000, G1500, and Virtual Storage Platform F1500 Hardware Guide