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Intel® RAID Adapters RS3P4TF160F and RS3P4MF088F Hardware User Guide
8.
Intel® RAID Maintenance Free Backup AXXRMFBU7
8.1
Intel® RAID Maintenance Free Backup AXXRMFBU7
Intel RAID adapters provide reliability, high performance, and fault-tolerant disk subsystem management. A
complete fault-tolerant strategy requires protection of all data, including the unwritten cached data in the
RAID card's RAM cache. If power is lost, the data in the RAM cache is lost. To avoid losing this data, a RAID
Maintenance Free Backup Unit (RMFBU) can be added to the configuration.
During normal system operation, the RMFBU monitors the voltage level of the DRAM of the Intel RAID
adapter. If the voltage drops below a predefined level due to an AC power failure or brief power outage, the
RMFBU protects the integrity of the cached data by providing sufficient back-up power to offload the data
from the RAID RAM to the NAND flash. When the voltage level returns to an acceptable level, the RAID RAM
is recovered from flash, and all pending writes to storage devices are completed without losing any data.
The cache memory available on Intel RAID adapters can improve the overall system performance. Writing
data to the adapter's cache memory is much faster than writing data to a storage device. Write operations
appear to complete very quickly at the software-application level. Intel RAID adapters write the cached data
to the storage device when system activity is low or when the cache is getting full.
The risk of using write-back cache is that the cached data can be lost if the AC power fails before it is written
to the storage device. This risk factor is eliminated when the Intel RAID adapter has an RMFBU installed. In
addition, the RMFBU provides an alternative to using an uninterruptible power supply (UPS) or can act as a
second level of fault tolerance when used with a UPS.
Furthermore, the RMFBU eliminates the need for lithium ion (Li-Ion) batteries traditionally used to protect
DRAM cache memory on PCI RAID adapters. Meaning, this is a greener and lower total cost cache protection
solution. Also, the RMFBU has built-in functionality to charge the capacitor adapter automatically and to
communicate status information such as voltage, temperature, and current to the host server system.
The Intel RAID Maintenance Free Backup AXXRMFBU7 is a kit consisting of an FBU345 super capacitor bank,
a plastic bracket to attach the super capacitor bank to the chassis, and two extender cables (one 605 mm
long and the other 930 mm long).
The FBU345 consists of a bank of electric double-layer capacitors (EDLC) or super capacitors that are
capable of storing a high amount of electric energy while active. If a power failure occurs, the FBU345
provides the power needed for the data offload. It also has an over-temperature detection circuitry and a
discharge circuitry. This circuitry discharges the capacitors while disconnected from the RAID adapter or
when the system on which it is installed on is turned off.
8.2
FBU345 Specifications and Layout
Table 11
shows the specifications for the FBU345 supercap.
dimensions and pin description.
Item
Super capacitor adapter operating temperature
Super capacitor adapter storage temperature
Rated voltage
Surge voltage
Super capacitor adapter capacity
Rated energy
Super capacitor adapter charge time
Super capacitor adapter shelf life
Table 11. FBU345 Specifications
Figure 15
shows the same device followed by its
Value
0–55 °C
0–70 °C
13.5 VDC
14.25 VDC
7.6 F
0.04 Wh
Approximately 2 minutes
3 years
37
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