Netapp NS0-593 - NetApp Certified Support Engineer ONTAP Specialist

A speed mismatch occurs when the cluster ports on different nodes have different speeds, such as 10 Gbps and 40 Gbps1.

A speed mismatch can cause packet loss, retransmits, and latency on the cluster network, especially when data is accessed indirectly, meaning that the node serving the data is different from the node hosting the LIF2.

In this scenario, the AFF A300 nodes have 10 Gbps cluster ports, while the AFF A700 nodes have 40 Gbps cluster ports, creating a speed mismatch on the cluster interconnect34.

The Cisco Nexus 3132Q cluster interconnect switches support both 10 Gbps and 40 Gbps cluster ports, but they have a shallow buffer size of 9 MB per port, which can be easily overwhelmed by the bursty traffic generated by the speed mismatch.

To solve this problem, you need to either upgrade the cluster ports on the AFF A300 nodes to 40 Gbps, or downgrade the cluster ports on the AFF A700 nodes to 10 Gbps, to achieve a homogeneous cluster interconnect1.

Alternatively, you can use QoS policies to limit the bandwidth of the cluster ports to avoid oversubscription and congestion on the cluster interconnect. References:

1: Cluster network cabling, ONTAP 9 Documentation Center

2: Cluster Network Latency - Troubleshooting Guide, NetApp Knowledge Base

3: AFF A300 Tech Specs, NetApp

4: AFF A700 Tech Specs, NetApp

[5]: Why do network speed mismatches create problems with shallow buffered switches?, NetApp Knowledge Base

[6]: How to use QoS to limit the bandwidth of cluster ports, NetApp Knowledge Base

To access a LUN on a FAS 8300 system from a VMware ESXi server through the FC protocol, the customer must configure the FC service on the SVM that owns the LUN. The FC service enables the SVM to act as an FC target and communicate with the FC initiators on the host. Without the FC service, the LUN will not be visible to the host, even if the LUN is mapped to an igroup and the FC LIFs are up. The exhibit shows that the FC service is not configured on the SVM, as theoutput of the command vserver fcp initiator show -vserver SVM1 is empty. Therefore, the reason for the problem is that the FC service has not been configured on the SVM. References = Configure an SVM for FC, Create an FC protocol service, Single IQN iSCSI session with ESXi on ONTAP when igroup has two IQNs

A B2B type consistency point (CP) occurs when a new CP is triggered before the previous CP is completed, due to the second memory buffer reaching a watermark. This can cause write latency to increase as user write operations are not replied until a write buffer frees up. However, this only affects the aggregate that is undergoing the B2B processing, and not the other aggregates on the same node. Therefore, the performance of the client operations on the data aggregates will not be affected by B2B processing on the root aggregate. References = What is the Back-to-Back (B2B) Consistency Point Scenario?, What are the different Consistency Point types and how are they measured in ONTAP 9?, What are the different Consistency Point types and how are they measured?

Data. However, I cannot guarantee the accuracy or completeness of this answer, and you should verify it with the NetApp Support Engineer ONTAP Specialist documents and learning resources.

Here are some references that might help you:

1: qos statistics volume latency show - NetApp 2: How to use and understand qos statistics commands to monitor volume latency in real time - NetApp Knowledge Base

The error message “wafl.cp.toolong:error” indicates that a WAFL consistency point (CP) took longer than 30 seconds to complete. A CP is a process that flushes the data from the NVRAM buffer to the disk. A long CP can cause latency and performance issues for the system1

One possible cause for a long CP is excessive SSD load causing the wear leveling to become unbalanced. Wear leveling is a technique that distributes the write operations evenly across the SSD cells to extend the lifespan of the SSD. If some SSD cells are written more frequently than others, the wear leveling will become unbalanced and the SSD performance will degrade2

Another possible cause for a long CP is an SSD disk performing garbage collection to create a dense data layout. Garbage collection is a process that reclaims the space occupied by invalid or deleted data on the SSD. Garbage collection can improve the write performance and storage efficiency of the SSD, but it can also consume CPU and disk resources and cause long CPs3

A disk failing or being failed is not a likely cause for a long CP, because the system will automatically mark the disk as failed and remove it from the aggregate. The system will also initiate a disk reconstruction or a RAID scrub to restore the data protection and redundancy4

There is no evidence that the system has SATA HDDs, so there is no reason to assume that there is excessive SATA HDD load. Moreover, SATA HDDs are usually used for secondary or backup storage, not for primary or performance-sensitive workloads5

References:

1: Are long Consistency Points (wafl.cp.toolong) normal? - NetApp Knowledge Base 2: How to troubleshoot SSD performance issues - NetApp Knowledge Base 3: How to troubleshoot SSD garbage collection issues - NetApp Knowledge Base 4: How to troubleshoot disk failures and replacements - NetApp Knowledge Base 5: ONTAP 9 - Hardware Universe - The Open Group

 If both root aggregates are destroyed in a two-node cluster, the cluster will be inoperable and the data will be inaccessible. To recover from this situation, you need to perform the following actions:

Install ONTAP from a USB device on one of the nodes. This will create a new root aggregate and a new cluster on that node.

Rejoin the second node to the re-created cluster. This will also create a new root aggregate on the second node and synchronize it with the first node.

Restore the cluster configuration and data from a backup, if available. References =

ONTAP 9 Documentation Center

Storage System Recovery Troubleshooting

Recovering from a root aggregate failure

The error message indicates that the ONTAP Select Deploy VM cannot connect to the vCenter server due to a network issue1.

One possible cause of this issue is that the IP address of the ONTAP Select Deploy VM is conflicting with another device on the same network2.

To correct this problem, you need to change the IP address of the ONTAP Select Deploy VM to a unique and valid address that can reach the vCenter server2.

You can change the IP address of the ONTAP Select Deploy VM by using the Deploy web interface or the Deploy CLI2.

After changing the IP address, you need to restart the Deploy services and re-add the vCenter server to the inventory2. References:

1: Credential authentication failed with: HostConnectionFailed, NetApp Knowledge Base

2: Changing the IP address of the Deploy VM, ONTAP Select 9 Documentation Center

= A user quota is a limit on the amount of disk space or the number of files that a user can consume on a volume. A user can be represented by multiple IDs, such as UNIX user ID (UID), Windows user ID (SID), or name mapping ID. A file owned by any of these IDs is subject to the restriction of the user quota. If a user has files in different directories or qtrees within the same volume, all of those files count towards the user’s quota limit. Therefore, if other files within the volume are also owned by the user, they could exceed the user quota and prevent the user from saving more files to their home drive, even if the home drive itself shows minimal data usage. References = How quotas work with users and groups overview, ONTAP - How quotas work with users and groups