DCSW flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Concurrently maintainable
- A design property where any planned maintenance activity on one infrastructure path can be performed without affecting the IT load, typically achieved with physically separate redundant paths.
- Fault tolerant
- A design property where any single unplanned failure in the infrastructure does not interrupt the IT load, requiring redundant and independent paths at every level.
- Uptime Tier III
- Certification level requiring concurrently maintainable infrastructure with no shutdown for planned maintenance; distinct from TIA-942 Rated-3 and assessed by Uptime Institute.
- PUE
- Power usage effectiveness equals total facility power divided by IT equipment power; a value of 1.0 is theoretical best and overhead comes from cooling and electrical losses.
- Double-conversion UPS
- An online UPS that converts AC to DC and back to AC, isolating the load from all utility disturbances including sags, surges, and frequency variation.
- Static transfer switch
- A solid-state device that transfers a load between two power sources in a few milliseconds, faster than a mechanical automatic transfer switch.
- Generator walk-in
- The gradual ramp of UPS rectifier load after a generator picks up, which must be matched to generator step-loading capability to avoid stalling.
- Affinity laws
- For pumps and fans, flow varies linearly with speed, pressure with the square, and power with the cube of speed.
- Low delta-T syndrome
- A condition where chilled water return temperature is lower than design, reducing plant capacity, often caused by coil fouling or three-way valve misuse.
- Water-side economizer
- A cooling mode using a cooling tower or fluid cooler to produce chilled water without running the chiller when outdoor wet-bulb temperature is low enough.
- ASHRAE recommended envelope
- The inlet air temperature and humidity range for efficient, reliable IT operation, roughly 18-27 °C and 8-60% relative humidity for Class A1.
- Hot-aisle containment
- An enclosure over the hot aisle that captures exhaust air and returns it to air handlers, preventing mixing with cold-aisle supply air.
- CRAH unit
- A chilled-water air handling unit with no compressor; it uses chilled water from a central plant and a fan to cool IT equipment.
- Rack Cooling Index
- A metric quantifying how well rack inlet temperatures stay within ASHRAE recommended or allowable limits; higher values indicate better airflow management.
- MDA
- Main distribution area in structured cabling, the space housing the core switches and main cross-connect for the data center.
- OM4 multimode fiber
- Laser-optimized multimode fiber supporting 10GBASE-SR to about 400 m and 40/100GBASE-SR to shorter distances in data center backbones.
- Spine-leaf architecture
- A two-layer network topology where every leaf switch connects to every spine switch, providing predictable low-latency east-west traffic.
- Pre-action sprinkler
- A water-based suppression system that requires two events, detection and a sprinkler head activation, before water enters the piping, reducing accidental discharge risk.
- Cross-zoning
- A suppression release logic requiring two independent detectors to alarm before agent discharges, reducing false discharge risk in a data hall.
- Room integrity test
- A door fan test that measures enclosure leakage to verify the space can hold the suppression agent concentration for the required hold time.
- Anti-passback
- An access control rule preventing a credential from being used to enter twice without an intervening exit, reducing card sharing and tailgating.
- Mantrap
- An interlocking two-door entry where only one door can open at a time, preventing piggybacking into a secure data hall.
- Multi-factor authentication
- Access control requiring two or more independent credential types, such as a card plus a PIN or biometric, to verify identity.
- Integrated systems test
- A commissioning test proving that electrical, mechanical, and controls systems operate together under load, including generator and UPS transitions.
- Method of procedure
- A document describing step-by-step work on critical infrastructure, including prerequisites, rollback steps, and approvals before execution.
- Infrared thermography
- A predictive maintenance technique using thermal imaging to detect loose electrical connections and overheating before failure.
- Recovery time objective
- The maximum acceptable time to restore a critical process after disruption, derived from a business impact analysis.
- Recovery point objective
- The maximum acceptable data loss measured in time, determining whether synchronous or asynchronous replication is required between sites.
- Availability in nines
- Uptime expressed as a percentage: 99.9% allows about 8.77 hours downtime per year, 99.99% about 52.6 minutes.
- Hot site
- A recovery facility with live replicated infrastructure and data, enabling rapid failover with minimal downtime and near-zero data loss.
- Business impact analysis
- A process identifying critical business processes and their dependencies, used to set recovery time and recovery point objectives.
- ISO/IEC 27001
- An international standard for information security management systems, requiring risk assessment, controls, and continuous improvement.