Dell PowerVault MD3000i Hardware Owner's Manual

Also see for PowerVault MD3000i: Getting started Tuning guide System installation guide User guide Information update

Contents

Dell PowerVault MD3000i Hardware Owner's Manual Manual pdf 24 page image

24 About Your SystemCache Functions and FeaturesCache MirroringThe cache mirroring function copies accepted host-write data from theprimary controller to the partner controller. This action ensures that host-write data is safely mirrored to the partner controller before successfulcompletion status is returned to the host. If a controller fails, the survivingcontroller safely retains all mirrored data. Cache mirroring is enabled bydefault.Write-Back CacheWrite-back cache is a caching strategy whereby write operations result in acompletion signal being sent to the host operating system as soon as thecache receives the data to be written. The target physical disk will receive thedata at a more appropriate time in order to increase controller performance.In dual-active controller configurations with write-back caching enabled, thewrite data is always copied to the cache of the second controller beforecompletion status is issued to the host initiator. Write Back is enabled bydefault.Write-Through CacheWrite-through cache is a caching strategy whereby data is written to thephysical disk before completion status is returned to the host operatingsystem. Write-through cache is considered more secure than write-backcache, since a power failure is less likely to cause loss of data. The RAIDcontroller automatically switches to write-through if cache mirroring isdisabled or if the battery is missing or has a fault condition.NOTE: Write cache settings are not user-configurable.Power Supply and Cooling Fan FeaturesYour RAID enclosure supports two integrated, hot-pluggable powersupply/cooling fan modules. Both modules must be installed to ensure propercooling. Each module contains two separate cooling fans. The enclosurerequires at least three of the cooling fans to operate to avoid overheating.