NS0-093 Exam Dumps : NetApp Accredited Hardware Support Engineer

 Understanding a Single PHY Down Issue:

In SAS environments, a PHY represents a physical layer connection between devices.

When a single PHY reports a "down" status, it typically indicates an issue with the physical connectivity or the associated hardware.

 Cause 1: Improperly Seated Cable

If the SAS cable is not properly seated in the port, the connection for one or more PHYs may fail.

Reseating the cable on both ends (controller and shelf) often resolves the issue.

 Cause 2: Defective Cable

A damaged or faulty SAS cable can cause PHY errors.

Replacing the cable and verifying the connection resolves the issue in this case.

 Why Other Options Are Not Likely:

B. Outdated IOM firmware: While outdated firmware can cause other issues, it rarely affects only a single PHY.

D. Offline shelf: If an entire shelf is offline, more than one PHY would typically be affected, as multiple connections are involved in SAS stacks.

 NetApp Reference Documentation:

Found in the "ONTAP SAS Cabling Guide" and "Shelf Troubleshooting Guide". These documents detail troubleshooting for PHY errors and common SAS hardware issues.

In a SAS stack of shelves, the connection between the expander and the disk uses a point-to-point topology.

Point-to-Point:

Each SAS disk in a shelf connects directly to the expander using a dedicated channel. This ensures that communication between the disk and expander is independent of other disks, improving performance and reliability.

Why SAS Uses Point-to-Point:

SAS (Serial Attached SCSI) eliminates the shared bandwidth limitations of traditional bus architectures (e.g., arbitrated loop or ring) by dedicating a connection to each device.

Key Details:

A. arbitrated loop:

Arbitrated loop is a topology used in Fibre Channel systems, not SAS.

C. loop:

SAS does not use loop-based communication; this is typical of older technologies like SCSI Parallel Interface (SPI).

D. ring:

Ring topology is not used in SAS stacks.

Why Other Options Are Incorrect:

"NetApp SAS Shelf and Disk Configuration Guide" specifies point-to-point communication between expanders and disks in SAS environments.

References:

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.