Dell POWERVAULT MD3620I - Manual (Page 36)

36 Planning: RAID Controller Modules
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 either cache mirroring is disabled or the battery is missing or
there is a fault condition.
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