The customer has two distinct requirements that can be met by creating a single Snapshot policy with two different schedules.

1. Four-Month Retention: The first requirement is for a local retention time of at least four months. This is best achieved by creating a weekly schedule within the Snapshot policy and setting its retention period to 122 days (approximately four months). This provides long-term recovery points without consuming excessive space.

2. One-Week Immutability: The second requirement is to protect one week of retention from deletion by ransomware or administrators. This is accomplished by using NetApp's SnapLock feature. A daily schedule can be configured to set a SnapLock (WORM) retention period of 7 days on the daily Snapshot copies, making them immutable for that duration.

Combining these two settings in one policy effectively meets both customer objectives.

A. Enable Autonomous Ransomware Protection (ARP) on the volume.

ARP is a reactive feature that creates locked Snapshot copies after it detects a potential ransomware attack. It does not guarantee a proactive, one-week protected retention as part of a standard policy.

C. Create a Snapshot policy with the maximum daily snapshots set to 122.

While this provides four months of retention, keeping 122 daily snapshots is generally less space-efficient for long-term retention than a tiered policy using weekly or monthly copies as described in option B.

1. NetApp Technical Report 4572: Ransomware Protection Using NetApp ONTAP Technologies, Page 10, Section: "ONTAP SnapLock".

Quote: "SnapLock for SnapVault copies provides the ability to make Snapshot copies immutable for a specified retention period... This feature prevents the Snapshot copies from being deleted either accidentally or maliciously before the retention period expires." This document confirms that SnapLock is the correct technology to protect Snapshot copies from deletion (supporting option D).

2. NetApp ONTAP 9 Documentation Center, Command Reference, snapshot policy create.

Details: The documentation for this command shows the parameters for creating schedules within a policy. It includes -schedule (e.g., daily, weekly), -count (number of copies to keep), and -retention-period (duration to keep copies). It also details the -snaplock-period parameter, which can be applied to a specific schedule. This confirms that a single policy can have a weekly schedule with a long retention period (Option B) and a daily schedule with a SnapLock period (Option D).

3. NetApp ONTAP 9 Documentation Center, Data protection, "Create a Snapshot policy".

Details: This guide explains that a Snapshot policy defines when to create Snapshot copies and how many copies to retain. It states, "A Snapshot policy can have up to five schedules with different retention periods and labels." This supports the creation of a policy with both a daily schedule for SnapLock and a weekly schedule for long-term retention.