System Password Reset; Cache Functions And Features; Cache Mirroring; Write-Back Cache - Dell POWERVAULT MD3620I Owner's Manual

System Password Reset

To reset a forgotten password, push and hold down the password reset switch
for at least 5 seconds. The password is deleted. See Figure 3-1 to locate the
password reset switch.
The RAID controller module allows you to change the password. For more
information about setting your password, see "Setting a Password" on page 73.
NOTE:
The reset switch can be accessed by using a small object, such as the tip of
a pen.

Cache Functions and Features

Cache Mirroring

Cache mirroring 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. By default, cache mirroring is enabled in duplex systems
and disabled in simplex systems.

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 duplex system configurations
with write-back cache and cache mirroring enabled, the write data is always
mirrored to the cache of the second controller before completion status is
issued to the host initiator. For simplex systems, if cache mirroring is enabled
write-back cache is suspended.
CAUTION:
Running a simplex system with write-back cache enabled, carries all
inherent risks associated with a non-redundant system. In case of a catastrophic
controller failure, data loss occurs.
Planning: RAID Controller Modules
35