Dell Unity XT asynchronous replication for block resources can be configured using a built-in periodic timer or by associating the replication session with a snapshot schedule. While the built-in timer has a maximum Recovery Point Objective (RPO) of 24 hours, a greater RPO can be achieved by using a snapshot schedule to trigger the replication sync. The snapshot schedule allows for a recurring hourly interval to be set. The maximum value for this recurring interval is 168 hours, which is equivalent to 7 days. Therefore, the maximum configurable interval-based RPO for a block-asynchronous replication session is 7 days.

A. 24 hours

This is the maximum RPO when using the replication session's native periodic timer, but it is not the overall maximum possible when using a snapshot schedule to control synchronization.

B. 14 days

While a calendar-based schedule could be created to run bi-weekly, the maximum configurable interval for a snapshot schedule is 168 hours (7 days), which represents the highest defined RPO frequency.

D. 48 hours

This is a valid RPO that can be configured using a snapshot schedule (e.g., "repeat every 48 hours"), but it is not the maximum configurable value.

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1. Dell Unity Family Unisphere Command Line Interface User Guide (Version 5.2)

Reference: Page 218, create -snapSchedule command description.

Quote/Content: In the description for the -repeatEvery parameter, the guide specifies the valid range for an hourly schedule: "For hours, specify a value from 1 to 168." (168 hours = 7 days). This confirms the maximum configurable hourly interval for a snapshot schedule.

2. Dell White Paper: Dell Unity: Replication Technologies

Reference: Page 16, Section "Asynchronous Replication".

Quote/Content: "It is also possible to use snapshot schedules to trigger synchronization. When a snapshot schedule is used, a new snapshot is created based on the schedule, and this snapshot is replicated to the destination." This document confirms that snapshot schedules are a valid method for controlling asynchronous replication sessions, thereby making their limits applicable to the session's effective RPO.