Dell MD3200 Cache Functions and Features, Cache Mirroring, Write-Back Cache, Write-Through Cache

Cache Functions and Features

Cache Mirroring

Cache mirroring function copies accepted host-write data from the primary controller to the partner controller. This action ensures that host-write data is safely mirrored to the partner controller before successful completion status is returned to the host. If a controller fails, the surviving controller safely retains all mirrored data. Cache mirroring is enabled by default.

Write-Back Cache

In Write-back Cache, write operations result in a completion signal being sent to the host operating system as soon as the cache receives the data to be written. The target physical disk receives the data at a more appropriate time in order to increase controller performance. In dual-active controller configurations with Write-back Caching enabled, the write data is always mirrored to the cache of the second controller before completion status is issued to the host initiator. Write-Back Cache is enabled by default unless cache mirroring is disabled.

Write-Through Cache

In write-through cache, data is written to the physical disk before completion status is returned to the host operating system. Write-through cache is considered more robust than write-back cache, since a power failure is less likely to cause loss of data. The RAID controller automatically switches to write-through if cache mirroring is disabled or if the battery is missing or has a fault condition.

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Planning: RAID Controller Modules