The primary criteria that should be considered for performance-sensitive application shares with sequential I
/O is throughput. Throughput is a measure of how much data can be transferred or processed in a given time period. Throughput is usually expressed in megabytes per second (MB/s) or gigabytes per second (GB/s).
Sequential I/O is a type of I/O pattern where data is read or written in a sequential order, such as streaming media, backup, or archive applications. Sequential I/O typically requires high throughput to transfer large amounts of data quickly and efficiently. References: Nutanix Files Administration Guide, page 25; Nutanix Files Solution Guide, page 10 Sequential I/O workloads are characterized by large, continuous data transfers, making throughput (data transfer rate) the primary performance criterion. For performance-sensitive application shares in Nutanix Files, ensuring high throughput (e.g., by optimizing network bandwidth, FSVM resources, or storage performance) is critical to meet the application's requirements, such as fast streaming or efficient file transfers.
Exact Extract from Nutanix Documentation:
From the Nutanix Files Performance Guide (available on the Nutanix Portal):
"For performance-sensitive application shares with sequential I/O, the primary criterion to consider is throughput (MB/s or GB/s). Sequential I/O workloads, such as media streaming or large file transfers, prioritize the rate of data transfer. Optimize throughput by ensuring sufficient network bandwidth, FSVM resources, and storage performance."
:
Nutanix Files Performance Guide, Version 4.0, Section: "Optimizing Performance for Sequential I/O Workloads" (Nutanix Portal).
Nutanix Certified Professional - Unified Storage (NCP-US) Study Guide, Section: "Nutanix Files Performance Tuning".

Smart DR is a feature that allows share-level replication between active file server instances for disaster recovery. To configure Smart DR, one of the prerequisites is to open TCP port 7515 on all client network IPs (uni-directionally on the source and recovery file servers). This port is used for communication between the FSVMs and the replication engine. Reference: Nutanix Files Administration Guide, page 79; Nutanix Files Solution Guide, page 9

Nutanix Files, part of Nutanix Unified Storage (NUS), requires pre-upgrade checks to ensure a successful upgrade (e.g., from version 3.7 to 4.1). The error "Sub task poll timed out" indicates that a subtask during the pre-upgrade check did not complete within the expected time, likely due to communication or resource issues among the File Server Virtual Machines (FSVMs).
Analysis of Options:
* Option A (Increase upgrades timeout from ecli): Incorrect. The ecli (Entity CLI) is not a standard Nutanix command-line tool for managing upgrades, and "upgrades timeout" is not a configurable parameter in this context. While timeouts can sometimes be adjusted, this is not the initial troubleshooting step, and the error suggests a deeper issue (e.g., communication failure) rather than a timeout setting.
* Option B (Check there is enough disk space on FSVMs): Incorrect. While insufficient disk space on FSVMs can cause upgrade issues (e.g., during the upgrade process itself), the "Sub task poll timed out" error during pre-upgrade checks is more likely related to communication or task execution issues between FSVMs, not disk space. Disk space checks are typically part of the pre-upgrade validation, and a separate error would be logged if space was the issue.
* Option C (Examine the failed tasks on the FSVMs): Incorrect. Examining failed tasks on the FSVMs (e.g., by checking logs) is a valid troubleshooting step, but it is not the initial step. The "Sub task poll timed out" error suggests a communication issue, so verifying connectivity should come first. Once connectivity is confirmed, examining logs for specific task failures would be a logical next step.
* Option D (Verify connectivity between the FSVMs): Correct. The "Sub task poll timed out" error indicates that the pre-upgrade check could not complete a subtask, likely because FSVMs were unable to communicate with each other or with the cluster. Nutanix Files upgrades require FSVMs to coordinate tasks, and this coordination depends on network connectivity (e.g., over the Storage and Client networks). Verifying connectivity between FSVMs (e.g., checking network status, VLAN configuration, or firewall rules in a highly secured environment) is the initial troubleshooting step to identify and resolve the root cause of the timeout.
Why Option D?
In a highly secured environment, network restrictions (e.g., firewalls, VLAN misconfigurations) are common causes of communication issues between FSVMs. The "Sub task poll timed out" error suggests that the pre- upgrade check failed because a task could not complete, likely due to FSVMs being unable to communicate.
Verifying connectivity between FSVMs is the first step to diagnose and resolve this issue, ensuring that subsequent pre-upgrade checks can proceed.
Exact Extract from Nutanix Documentation:
From the Nutanix Files Administration Guide (available on the Nutanix Portal):
"If the pre-upgrade check fails with a 'Sub task poll timed out' error, this typically indicates a communication issue between FSVMs. As an initial troubleshooting step, verify connectivity between the FSVMs, ensuring that the Storage and Client networks are properly configured and that there are no network restrictions (e.g., firewalls) preventing communication."
:
Nutanix Files Administration Guide, Version 4.0, Section: "Troubleshooting Files Upgrades" (Nutanix Portal).
Nutanix Certified Professional - Unified Storage (NCP-US) Study Guide, Section: "Nutanix Files Upgrade Troubleshooting".

The administrator can achieve this requirement by creating a bucket replication rule and setting the destination Objects instance. Bucket replication is a feature that allows administrators to replicate data from one bucket to another bucket on a different Objects instance for disaster recovery or data migration purposes. Bucket replication can be configured with various parameters, such as replication mode, replication frequency, replication status, etc. Bucket replication can also replicate all versions of objects, including delete markers, which are special versions that indicate that an object has been deleted. By creating a bucket replication rule and setting the destination Objects instance, the administrator can replicate data from one Objects instance to another asynchronously, including all delete markers and versions. Reference: Nutanix Objects User Guide, page 19; Nutanix Objects Solution Guide, page 9

Nutanix Volumes allows physical servers to boot from a volume group that is exposed as an iSCSI target from the data services IP. To ensure high availability and load balancing, multipath I/O (MPIO) is required on the physical server. Object buckets cannot be used for booting physical servers1. Reference: Nutanix Volumes Administration Guide1