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62 Sun Enterprise 220R Server Owner’s Guide • October 1999
About Reliability, Availability, and
Serviceability Features
Reliability, availability, and serviceability are three aspects of a system’s design
contributing to continuous operation and minimizing system downtime for service.
Reliability refers to a system’s ability to operate continuously without failures and to
maintain data integrity. System availability refers to the percentage of time that a
system remains accessible and usable. Serviceability relates to the time it takes to
restore a system to service following a system failure. Together, reliability,
availability, and serviceability provide for near continuous system operation.
To deliver high levels of reliability, availability, and serviceability, the system offers
the following features:
■ Error correction and parity checking for improved data integrity
■ Easily accessible status indicators
■ Hot-pluggable disk drives
■ Support for RAID 0, 1 storage configurations on internal drives
■ Support for RAID 0, 1, 0 +1, and 5 storage configurations on external disk drives
■ Redundant power supply support
■ Hot-swappable power supplies
■ Four different levels of system diagnostics
Error Correction and Parity Checking
Error-correcting code (ECC) is used on all internal system data paths to ensure high
levels of data integrity. All data that moves between processors, I/O, and memory
have end-to-end ECC protection.
The system reports and logs correctable ECC errors. A correctable ECC error is any
single-bit error in a 64-bit field. Such errors are corrected as soon as they are
detected. The ECC implementation can also detect double-bit errors in the same
64-bit field and multiple-bit errors in the same nibble (4 bits).
In addition to providing ECC protection for data, the system offers parity protection
on all system address buses. Parity protection is also used on the PCI and SCSI
buses, and in the UltraSPARC CPU’s internal and external cache.