HP D7171A - NetServer - LPr Manual page 6

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commonplace in DRAM cells, cause data to be stored incorrectly in a memory location, but
subsequent accesses can correctly store data into that cell. With properly tuned hardware
and software, occurrences of soft errors should be months or possibly years apart. In
reality, the environment and other hardware and software conflicts can cause noise or
contention that may precipitate more frequent random memory errors.
To protect the server from data loss associated with these errors, HP offers ECC memory
scrubbing as a diagnostic and repair tool. Basic ECC memory detects and corrects single-
bit memory errors, however, the errors themselves still remain in RAM. Each time the bad
data bit is accessed, it must be re-corrected by the memory controller. Two versions of
memory scrubbing are available—proactive and reactive. Reactive memory scrubbing
improves on basic ECC memory by writing the corrected data to RAM, after the error
occurs. Proactive memory scrubbing scrubs memory at pre-scheduled times or upon
demand. In either case, when a memory error is detected, the corrected data is written
back to RAM. This action ensures that all ECC memory errors will be logged and the bad
data bits are "scrubbed" from RAM.
The Pre-Failure Warranty covers the replacement of Single In-Line or Dual In-Line Memory
Modules (SIMMs or DIMMs) used in the server's main memory when the predefined
thresholds for correctable (soft) errors have been exceeded. Soft errors are recorded in the
Event log and a pre-failure alert is issued through HP TopTools for Servers.
Third-Party Memory
HP recognizes that purchasing or upgrading a mission-critical server requires confidence
that the server possesses high-quality memory compatible with the other components and
subsystems, so HP subjects its memory modules to a tough testing and qualification
process. HP quality and compatibility testing identifies the most reliable memory for use in
each HP NetServer. HP is confident of the quality and testing performed on its
components; therefore, the company warrants all products manufactured or distributed
by HP. HP warranties do not cover third-party memory, nor the damage that third-party
memory might cause.
Power Subsystem and Voltage Regulator Module
An uninterruptible power supply (UPS) is the most cost-effective step in increasing overall
system availability. Once you have protected and conditioned the power reaching the
system itself, the next component to consider is the power supply. Because power supplies
have a lower meantime between failure (MTBF) than digital electronic circuits, it is a good
idea to have redundancy built into the system. HP NetServers have redundant power
supplies included throughout the L Series.
The HP Pre-Failure Warranty for the power supplies provides an additional measure of
protection. The HP NetServer monitors the power supply voltages (+5v, +12v, -12v and
3.3v). Additionally, since a Voltage Regulator Modulator (VRM) powers each processor in a
HP NetServer, the system also monitors the voltage of each VRM.
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