NS0-093 Questions and Answers

When a WAFL inconsistency is detected, the first step is to stabilize the system before attempting any repairs or recovery.

Stabilize the System:

Ensure that the system is not experiencing ongoing hardware or software issues.

Avoid making changes to the affected aggregate or volume until the system is stable.

Assess the Impact:

Determine which aggregates or volumes are affected and the severity of the inconsistency.

Steps to Handle WAFL Inconsistency:

A. Run wafliron:

Running wafliron should only be done after stabilizing the system and under guidance from NetApp Support.

C. Force offline the affected aggregate:

Forcing an aggregate offline without proper assessment can lead to data loss.

D. Run a dump to null:

Dumping data is not relevant for resolving a WAFL inconsistency.

Why Other Options Are Incorrect:

"NetApp WAFL Troubleshooting Guide" specifies that stabilization is the first step after detecting inconsistencies.

NetApp Support documentation provides guidelines for handling WAFL inconsistencies safely.

References:

When a node fails to boot and loads the previous version of ONTAP, it usually indicates that the primary boot location is incorrect. To resolve this:

Enter the LOADER Prompt:

Interrupt the boot process to access the LOADER prompt.

Set the Primary Kernel URL:

Use the following command:

Steps to Boot the Correct ONTAP Version:setenv GX_PRIMARY_KERNEL_URL

Boot the Node:

Run the boot command to load the correct version.

B. From the loader prompt of nodeA1, run boot_backup:

Booting the backup image may result in an outdated version of ONTAP, not the desired version.

C. From the clustershell of the partner, run system node image modify:

Modifications to the ONTAP image must be done from the LOADER prompt, not the clustershell.

D. From the clustershell of nodeA1, run system node image modify:

NodeA1 cannot load ONTAP, so this command cannot be run.

Why Other Options Are Incorrect:

"ONTAP System Boot Guide" explains how to resolve boot issues using the LOADER prompt.

NetApp documentation on environment variables includes the use of GX_PRIMARY_KERNEL_URL.

References:

 Analyzing the Error in the Event Log:

The log entry indicates a medium error on a disk, suggesting an unrecoverable read issue.

While the RAID subsystem attempts to reconstruct unreadable data, this error might indicate a firmware issue or a compatibility problem with the disk.

 Why Reviewing Firmware and Known Issues Is Important:

Medium errors can sometimes result from outdated or incompatible firmware.

By reviewing firmware release notes and known issues for the disk model (NETAPP X381_HLBRE10TSDB in this case), you can identify if this is a known issue and resolve it by updating the firmware.

 Other Options:

Sanitize the disk (Option A): Not relevant here, as sanitization is used for secure data erasure.

Reseat the disk (Option B): Useful for addressing hardware seating issues, but not the first step here.

Diskcopy to a spare (Option D): This is a last-resort recovery step and not the primary action.

 NetApp Reference Documentation:

"ONTAP Disk Management Guide" and "Disk Firmware Release Notes" detail how to handle medium errors and update firmware.

The following ONTAP systems support both SSD and SAS disks:

Description:

The FAS2750 is part of NetApp's hybrid storage array product line.

It supports both SSDs for performance tiers and SAS disks for capacity tiers, making it suitable for mixed workloads.

1. FAS2750

Description:

The FAS8200 is an enterprise-level storage system that also supports hybrid configurations with both SSD and SAS drives.

This system is designed to handle high performance and capacity needs.

2. FAS8200

A. AFF C190:

The AFF C190 is an all-flash system and only supports SSDs. It does not support SAS disks.

C. AFF A220:

Like the AFF C190, the AFF A220 is also an all-flash system that supports SSDs only.

Why Other Options Are Incorrect:

NetApp "Hardware Universe" confirms drive support for FAS and AFF systems.

NetApp product documentation details supported disk types for hybrid and all-flash systems.

References:

To trigger an AutoSupport message in ONTAP, the following commands are valid:

What it does:This command manually triggers a complete AutoSupport message of type "all." This includes logs and system information from all subsystems.

How to use:

Run the command: autosupport invoke –node –type all

Replace with the name of the node for which you want to generate the AutoSupport message.

Why it's relevant:This is the primary method for triggering a full AutoSupport message manually. It is commonly used during troubleshooting to provide comprehensive system data to NetApp Support.

1. ::> autosupport invoke –node –type all

What it does:This command is specifically used to upload core files (e.g., kernel or user space cores) from a node to NetApp Support for analysis.

How to use:

Run the command: autosupport invoke-core-upload –node .

Replace with the name of the node for which you want to upload core files.

Why it's relevant:If there is a system panic or other critical issue, this command ensures that core files are included in the AutoSupport message for detailed analysis.

2. ::> autosupport invoke-core-upload –node

A. ::> autosupport history show-upload-details –node <nodename>:

This command displays the history of AutoSupport uploads but does not trigger a new AutoSupport.

B. ::> system node coredump upload –node <nodename>:

This command uploads coredumps directly to a support server but does not trigger an AutoSupport message.

Why Other Options Are Incorrect:

"ONTAP 9 AutoSupport Configuration Guide" confirms autosupport invoke as a valid command to trigger AutoSupport messages.

"ONTAP CLI Reference Manual" specifies autosupport invoke-core-upload for core file uploads.

References:

 FRUs on FAS9000 Supporting Replacement Without Takeover:

A (I/O Module): I/O modules can be replaced hot (without takeover) to maintain system uptime during hardware servicing.

D (NVRAM Module): NVRAM modules on FAS9000 can also be replaced without a node takeover, ensuring data integrity during replacement.

 Why Other Options Are Incorrect:

B (DCPM Module): The DCPM (Data Center Power Management) module is not hot-swappable and requires a node takeover.

C (Caching Module): The caching module is integrated and typically requires a node takeover or power-down for replacement.

 NetApp Reference Documentation:

Refer to the "NetApp FAS9000 Hardware Service Guide" for supported FRU replacement procedures and operational constraints.

When a volume is deleted in a NetApp ONTAP system, it is placed in the Volume Recovery Queue. By default, the volume remains in this recovery queue for 12 hours before being permanently deleted. This allows administrators to recover mistakenly deleted volumes within the set retention period.

Explanation of Default Behavior:

Volume Recovery Queue:

This is a feature in NetApp ONTAP that acts as a safety mechanism, providing a grace period for recovering deleted volumes.

The default retention period for volumes in the recovery queue is 12 hours, as confirmed by the NetApp KB: "How to use the Volume Recovery Queue."

How to Recover a Deleted Volume:

Administrators can recover a deleted volume as long as it remains in the recovery queue and the retention period has not expired.

Use the ONTAP CLI command:

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cluster::> volume recovery-queue recover -vserver -volume

This command restores the volume back to its original state.

How to Check the Volume Recovery Queue:

To view volumes in the recovery queue and their expiration times, use:

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cluster::> volume recovery-queue show

Changing the Default Retention Period:

While the default period is 12 hours, it can be adjusted by administrators to fit specific organizational requirements. This is done via system settings or policies.

Why the Other Options Are Incorrect:

B. 48 hours: Incorrect. The default retention period is not 48 hours; it is 12 hours by default.

C. 72 hours: Incorrect. While a custom configuration could allow this, it is not the default.

D. 24 hours: Incorrect. Although this was previously thought to be the default, NetApp documentation explicitly states it is 12 hours.

References:

NetApp Knowledge Base Article: "How to use the Volume Recovery Queue".

NetApp ONTAP Documentation: Volume Recovery and Data Management Procedures.

 What Is a Watchdog Timeout?

The watchdog is a software or hardware mechanism that monitors the system’s health and ensures it is operating correctly.

If the system fails to respond or update the watchdog timer within the specified time, the watchdog triggers a system panic to avoid further corruption or damage.

 Cause of Watchdog Timeout:

This usually occurs due to:

A hardware failure (e.g., CPU or memory issue).

A software bug causing a system hang or crash.

The panic ensures the system stops operation to preserve data integrity and aid in troubleshooting.

 NetApp Reference Documentation:

"ONTAP Troubleshooting Guide" and "Core Dump Analysis Guide" provide details on interpreting watchdog timeouts and recommended actions.

 Steps to Unfail a Disk in Maintenance Mode:

When a disk is marked as "failed," it is added to the Failed Disk Registry and marked as unusable by the system. Unfailing a disk involves removing it from this registry and resetting its state.

 Step 1: Remove the Disk from the Failed Disk Registry

Use the command: registry remove to delete the disk from the Failed Disk Registry. This clears its "failed" status.

 Step 2: Use the Disk Unfail Command

Execute the disk unfail command to reset the disk status and make it available for use.

 Key Notes:

After unfailing, the disk will be treated as a spare and must be reassigned or re-added to an aggregate.

If the disk remains failed after these steps, physical hardware issues may need to be addressed.

 NetApp Reference Documentation:

The "ONTAP Maintenance Mode Guide" and "Disk Management Guide" provide detailed instructions for handling failed disks and using the disk unfail command.

 Purpose of the -cfo-only true Option:

This option is used during the giveback process in a NetApp cluster to control which aggregates are returned to the original node.

By specifying -cfo-only true, only the data aggregates are given back to the original node, while the root aggregate remains with the takeover node.

 Use Case:

This command is helpful when you want to test the aggregate giveback functionality or if the root aggregate requires further investigation or maintenance before returning it to the original node.

 NetApp Reference Documentation:

The "ONTAP High-Availability Configuration Guide" and "Cluster Failover Management Guide" detail the behavior of the -cfo-only option during giveback scenarios.

To manually generate a kernel core file in ONTAP, the following commands can be used:

What it does:Reboots the specified node and generates a core dump before rebooting.

Example Usage:

1. ::> reboot –node –dump truereboot –node –dump true

What it does:Halts the specified node and generates a core dump before shutting down.

Example Usage:

2. ::> halt –dump true –node halt –dump true –node

What it does:Forces a panic on the specified node, which triggers a kernel core dump.

Example Usage:

3. ::> system node panic –node system node panic –node

A. SP> system power cycle:

This command reboots the system from the Service Processor but does not generate a core dump.

E. SP> system core:

This command displays core file information but does not generate a new core dump.

Why Other Options Are Incorrect:

NetApp "Kernel Core Dump Guide" explains the use of reboot, halt, and panic commands to trigger core dumps.

ONTAP CLI Reference includes the syntax for these commands.

References:

To recover an inconsistent aggregate, the following tools can be used:

What it does:This tool is used to perform a consistency check on WAFL metadata. It identifies and attempts to fix WAFL inconsistencies in aggregates.

When to use:Run wafl_check after identifying WAFL inconsistencies to repair minor metadata issues.

1. wafl_check

What it does:This tool repairs WAFL inconsistencies by reconstructing metadata. It is more powerful than wafl_check and should only be run under NetApp Support guidance, as improper use can result in data loss.

When to use:Use wafliron for severe WAFL inconsistencies that cannot be resolved by wafl_check.

2. wafliron

A. file check:

This is not a valid NetApp tool.

C. wafl snapiron:

While similar in name, snapiron is used for snapshot recovery, not aggregate recovery.

Why Other Options Are Incorrect:

"ONTAP Aggregate Troubleshooting Guide" details the usage of wafl_check and wafliron.

NetApp Support documentation provides guidelines for recovering inconsistent aggregates.

References:

To reset environment variables to factory settings, the set-defaults command is used. This command clears all customizations and restores the environment variables to their default values.

Command Syntax:At the LOADER prompt, type:

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set-defaults

Effect:This command resets all environment variables (e.g., boot arguments, diagnostic settings) to their original factory defaults.

B. unsetenv all:

This command clears all environment variables, but it does not restore them to factory defaults.

C. setenv factory:

This is not a valid command in NetApp systems.

D. wipeconfig:

This command is used to clear configuration and logs but does not reset environment variables.

Why Other Options Are Incorrect:

NetApp "System Configuration Guide" confirms the use of set-defaults for restoring environment variables to factory settings.

References: