MongoDB C100DBA - MongoDB Associate Database Administrator(Based on MongoDB 6.0 and 7.0+)

The most direct evidence that storage capacity is approaching exhaustion is high filesystem utilization and explicit operating-system errors showing that no space remains. Sustained disk utilization above 90% is a practical warning threshold because the deployment has little headroom for database growth, index builds, temporary files, journal activity, or operational spikes. The errno:28 No space left on device message is even stronger evidence: the operating system rejected a write because the relevant filesystem could not allocate additional space. The other choices can correlate with workload growth but do not specifically prove a capacity problem. Query execution time can increase because of poor indexes, cache misses, lock or ticket contention, or CPU pressure. A rising document count says nothing about remaining free space without knowing document size, index size, and volume capacity. Low read/write ticket availability reflects storage-engine concurrency pressure rather than filesystem capacity. Administrators should therefore monitor disk-used and disk-free metrics, alert well before full utilization, and investigate any ENOSPC-style log events immediately. B and D are the two storage-capacity indicators.

Study Guide reference/topic:Performance Monitoring and Tuning - disk capacity, storage metrics, alerts, and diagnostic logs.

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The --fork option starts mongod in daemon mode so the server process continues in the background. When --fork is used, MongoDB requires diagnostic output to be redirected through a logging destination such as --logpath or --syslog; the process cannot simply detach while continuing to use the normal foreground output stream. Option C supplies both --fork and a valid log path, while leaving the other server settings at their normal defaults unless they are configured elsewhere. Option A explicitly sets the default port but does not satisfy the logging requirement associated with --fork. Option B treats the literal word default as a filesystem path and does not provide the required log destination. Option D uses an unsupported --default switch. In production, MongoDB packages commonly use service managers such as systemd, and a configuration file is usually preferred over manually launching mongod with a long list of command-line options. Nevertheless, among the commands shown, C is the one that correctly daemonizes the server process and provides the logging configuration required for a successful fork.

Study Guide reference/topic:MongoDB Architecture and Core Operations - mongod startup, background execution, logging, and server configuration.

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