Dell PowerVault MD3000 - Manual (Page 18)

18
About Your System
Write-Through Cache
Write-through cache is a caching strategy whereby data is written to the physical disk before completion
status is returned to the host operating system. Write-through cache is considered more secure 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. Write-through cache results in lower performance.
NOTE:
Cache mirroring and write cache settings are not user-configurable.
Power Supply and Cooling Fan Features
Your RAID enclosure supports two integrated, hot-pluggable power supply/cooling fan modules. Both
modules must be installed to ensure proper cooling. Each module contains two separate cooling fans.
The enclosure requires at least three of the cooling fans to operate to avoid overheating.
CAUTION:
A power supply/cooling fan module can be removed from a powered-on enclosure for a maximum
period of no more than 5 minutes. Beyond that time, the enclosure may automatically shut down to prevent
damage to the enclosure and/or enclosure components.
A power supply/cooling fan module can be replaced without powering down the enclosure. For
information on removing and replacing the modules, see "Removing and Installing the Power
Supply/Cooling Fan Module" on page 62.
Figure 1-7 shows the power supply/cooling fan module features and LED indicators. Table 1-5 lists the
LED indicator descriptions.
Figure 1-7. Power Supply and Cooling Fan Module LED Features and Indicators
1 DC power LED 2 Power supply/cooling fan fault
LED 3 AC power LED
4 cooling fans (2) 5 on/off switch 6 AC power connector
1 4
5 6
2 3