DCNSA Level III
Server Maintenance cheat sheet
Every chapter's key points, formulas and definitions on one page, for the last week before the exam. Each heading links to the chapter that explains it.
Select server maintenance methods, procedures and tools
- Restore returns lost or corrupted data to a working state from a backup; recover is the broader return of a server or service to normal operation, which may also mean rebuilding configuration, reinstalling roles or failing over to another server.
- Preventive maintenance is planned work before any problem, predictive acts on an early warning sign in monitoring data, corrective fixes a fault that has already occurred, and periodic runs at fixed intervals regardless of the server's condition.
- The test between periodic and preventive is the trigger: purely the calendar is periodic, a deliberate plan to reduce risk is preventive.
- Maintenance covers every resource a server depends on: network, disks, time, memory and devices, not only its disks.
- A programme built on corrective maintenance alone is simply reacting to disasters; preventive and periodic work form the baseline, with predictive maintenance added where good monitoring data exists.
Key terms
- Disaster
- An event causing serious disruption or loss to server operations or data, large enough to threaten the organisation's ability to function until it is resolved.
- Loss
- Data or capability that has gone missing or become unusable, the specific harm a disaster or a lesser fault can cause.
- Restore
- Returning lost or corrupted data to a working state from a backup, the narrow, data-focused half of recovering from loss.
- Recover
- The broader process of returning a server or service to normal operation after a disruption, which may involve restoring data but also rebuilding configuration, reinstalling roles, or failing over to another server entirely.
- Maintenance
- The planned, ongoing work of keeping a server healthy and performing well, the preventive counterpart to the reactive work of recovering from a disaster once one has already happened.
- Preventive maintenance
- Planned, routine work carried out before a problem occurs, to reduce the chance of one happening at all: cleaning, checking connections, applying known-safe updates.
- Predictive maintenance
- Uses monitoring data and trends to anticipate a likely failure before it happens, acting on an early warning sign (rising error rates, a disk's SMART data degrading) rather than a fixed schedule.
- Corrective maintenance
- Carried out after a fault has already occurred, to fix it: replacing a failed drive, restoring a corrupted file, restarting a crashed service.
- Periodic maintenance
- Carried out at fixed, regular intervals regardless of the server's current condition, for example monthly patching applied on the same date every month whether or not any specific vulnerability has been flagged.
- Network
- Connectivity, bandwidth and network-related configuration, checked as part of the same discipline developed in Network Troubleshooting.
- Disks
- Storage capacity, health and performance, tracked over time (see the chapter on server monitoring) rather than checked only when a warning already appears.
- Time
- System clock accuracy, critical for authentication (a domain's Kerberos authentication fails if clocks drift too far apart), logging (events must be timestamped consistently to be useful) and scheduled tasks to function correctly.
- Memory
- Available RAM and memory-related performance, watched for the kind of gradual consumption that precedes a slowdown or a crash.
- Devices
- Attached hardware and peripherals, checked for failing components before they take a dependent service down with them.
The rest of the sheet covers
- Server maintenance procedures
- Server monitoring
- Maintaining Active Directory
- Maintaining virtual servers
- The maintenance document
- Worked examples
- Exam technique and revision
- Glossary