EXIN CDCS flashcards
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33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Availability formula
- Availability = MTBF / (MTBF + MTTR). It expresses the fraction of time a system is operational, where MTBF is mean time between failures and MTTR is mean time to repair.
- Tier III characteristic
- Concurrently maintainable: every component can be removed or replaced for planned maintenance without shutting down IT load. It uses dual power paths but only one is active at a time.
- Tier IV characteristic
- Fault tolerant: the site sustains an unplanned failure of any single component without affecting IT load. It provides two simultaneously active power paths and compartmentalized infrastructure.
- Tier II characteristic
- Redundant capacity components: critical systems include N+1 spares, but the site still needs a shutdown for some maintenance. It has a single distribution path with redundant components.
- 2N redundancy
- Two complete, independent systems each sized for full load, with no dependency between them. Failure of one system leaves the other fully capable of carrying the entire load.
- PUE definition
- Power Usage Effectiveness = total facility power divided by IT equipment power. A ratio of 1.0 means all power reaches IT; lower values indicate better energy efficiency, not higher availability.
- DCiE definition
- Data Centre Infrastructure Efficiency = 1 / PUE, expressed as a percentage. It is the reciprocal of Power Usage Effectiveness and represents the share of facility power delivered to IT equipment.
- WUE definition
- Water Usage Effectiveness = annual water consumption in litres divided by IT equipment energy in kWh. It quantifies cooling water intensity and complements PUE as a sustainability metric.
- Double-conversion UPS
- An online UPS rectifies mains to DC and inverts back to AC continuously, so the load always runs on conditioned power. It isolates IT from sags, surges, and frequency variation.
- Line-interactive UPS
- A UPS that conditions voltage with an automatic voltage regulator and transfers to battery on outage. It is cheaper than double conversion but offers less isolation from power quality problems.
- Hot aisle containment
- Physical enclosure of the hot aisle so hot exhaust air returns directly to the cooling units. It prevents mixing with cold supply air, improving delta-T and cooling efficiency.
- Rack Cooling Index
- RCI measures how well rack inlet temperatures comply with ASHRAE limits. RCI-high scores overheating risk; RCI-low scores overcooling. Values near 100% indicate good airflow management.
- ASHRAE inlet envelope
- Recommended range for IT equipment inlet air, roughly 18 to 27 degrees Celsius with humidity limits. Operating inside this envelope allows wider cooling setpoints and energy savings.
- RTO definition
- Recovery Time Objective: the maximum acceptable time to restore a service after disruption. It is derived from business impact analysis and drives redundancy and failover design choices.
- RPO definition
- Recovery Point Objective: the maximum acceptable amount of data loss measured in time. It determines backup frequency and whether replication must be synchronous or asynchronous.
- Business Impact Analysis
- A process that identifies critical business functions and quantifies the impact of their loss over time. Its outputs set recovery priorities, RTO, and RPO for IT services.
- Risk treatment options
- Four standard responses to identified risk: avoid the activity, mitigate or reduce likelihood/impact, transfer via insurance or contract, or accept and monitor the residual risk.
- Residual risk
- The risk remaining after controls have been applied. It must be documented, assigned an owner, and accepted formally, because controls rarely eliminate risk entirely.
- ISO/IEC 27001
- An international standard specifying requirements for an Information Security Management System. It uses a risk-based approach with controls for confidentiality, integrity, and availability of information.
- EN 50600 series
- European standard for data centre facilities and infrastructures. It defines availability and protection classes, covering power distribution, environmental control, security, and operational processes.
- ANSI/TIA-942
- A telecommunications infrastructure standard for data centres. It defines rated levels and addresses cabling, topology, redundancy, and site infrastructure for telecom spaces and data halls.
- Security zones
- Layered physical areas with progressively stricter access, such as perimeter, building, computer room, and rack. Each boundary requires its own access control and monitoring controls.
- Two-person rule
- A control requiring two authorized individuals to be present for sensitive actions or access to critical areas. It reduces insider threat and enables independent verification of activity.
- Least privilege
- A security principle granting users only the access needed for their role and no more. It limits the blast radius of compromised credentials and simplifies access reviews.
- Clean agent suppression
- Fire suppression using electrically non-conductive extinguishing agents that leave no residue, suitable for occupied IT spaces. Examples include inert gas blends and fluorinated ketones.
- VESDA detection
- Very Early Smoke Detection Apparatus: an aspirating system that continuously samples air through pipes to a laser detector. It detects incipient fire before visible smoke appears.
- Incident versus problem
- An incident is an unplanned interruption or degradation of service requiring rapid restoration. A problem is the underlying cause of one or more incidents, investigated through root cause analysis.
- Cold, warm, hot sites
- Disaster recovery site types ordered by readiness. Cold has space and power only, warm has partial equipment and data, hot is fully equipped with near-real-time data replication.
- DCIM system
- Data Centre Infrastructure Management software that tracks assets, connections, power chains, and capacity across the facility. It supports change planning and prevents overloading circuits or racks.
- BMS versus EPMS
- BMS monitors and controls building systems such as cooling and humidity. EPMS focuses on electrical power distribution, metering, breaker status, and UPS or generator performance.
- Lock-out tag-out
- A safety procedure isolating energy sources and applying personal locks and tags before maintenance. It prevents accidental energization and is mandatory for electrical work in data centres.
- Arc flash assessment
- A study calculating incident energy at electrical equipment, setting arc flash boundaries and required PPE. It informs labelling and safe work practices for energized equipment maintenance.
- Data sanitization levels
- NIST SP 800-88 defines clear, purge, and destroy. Clear removes data for reuse, purge protects against laboratory recovery, and destroy renders media unusable, each with differing assurance.