Dell Unity™ Family Unisphere® Command Line Interface User Guide

Manage snapshots

A snapshot is a virtual point-in-time image of the data within a storage resource that has changed since the last snapshot. Snapshots provide a record of the content in the targeted storage resource at a particular date and time, but are not mirror copies of the data. Periodically creating snapshots of file systems and LUNs provides an effective technique for meeting data protection and recovery requirements. Based on the importance and volatility of data within a storage resource, you can define recurring schedules that specify times and intervals for snapshot operations.

Use snapshots to perform the following:

Restore a storage resource to a previous point-in-time.
Access the contents of a snapshot to recover corrupted or accidentally deleted files and data.

To routinely take snapshots automatically, associate a snapshot with a schedule. Manage snapshot protection schedules explains how to configure schedules on the system. Each snapshot is identified by an ID.

NOTE:Snapshots do not provide a substitute for storage backup operations. Snapshots are not intended for recovering from disasters or the loss of physical equipment.

The following table lists the attributes for snapshots:

Table 1. Snapshot attributes
Attribute	Description
ID	ID of the snapshot.
Name	Name of the snapshot.
State	State of the snapshot. Valid values are: initializing ready faulted offline destroying
Attached	Indicates whether the snapshot is attached to a host. NOTE:This field is blank for file system snapshots.
Source	ID of the storage resource of which the system created the snapshot.
Source type	Type of storage resource of which the system created the snapshot.
Attach details	Comma-separated list of export paths or WWNs for attached snapshots.
Members	Comma-separated list of the member LUNs of the snapshot. NOTE:This field is blank for file system snapshots.
Source snapshot	For a snapshot of a snapshot, the ID of the parent snapshot.
Description	Snapshot description.
Creation time	Date and time when the snapshot was created.
Expiration time	Date and time when the snapshot will expire and be deleted from the system. Default is 7 days.
Last writable time	Last time the snapshot or its parent snapshot was detached.
Last refresh time	Indicates the last time that the snapshot was refreshed.
Created by	Name of the user, protection schedule, or backup process that created the snapshot. Valid values are: For manual snapshots created by a user, the user account name. For scheduled snapshots, the name of the protection schedule. For snapshots created by host backup software: NDMP—Indicates a snapshot created by using the Network Data Management Protocol (NDMP). VSS—Indicates a snapshot created by using the Microsoft Volume Snapshot Service (VSS), also called Shadow Copy or Previous Version. Snapshot Restore—Indicates a snapshot created automatically by the system when restoring a file system or VMware NFS datastore. You can use the snapshot to return the storage resource to the state it was in prior to the last restore.
Modified	Indicates whether the snapshot is or was previously attached to a snapshot mount point, or has shares. Valid values are: yes no
Allow auto-delete	Indicates whether or not the system can automatically delete the snapshot. Valid values are: yes no Default value is yes.
Size	Pool capacity consumed by the snapshot. NOTE:This field is blank for snapshots of consistency groups and VMware block applications.
Access	Indicates whether a file system snapshot is a read-only checkpoint, or read/write for user access.
IO limit	Comma-separated IO limit policy IDs for the attached snapshots of block-based storage resources. Members of a snapshot group can have different IO limit policy IDs.
Effective maximum IOPS	Dependant on the policy type. For a density-based policy, this value is the product of the maximum IOPS and the size of the attached snapshot. This is a read-only attribute.
Effective maximum KBPS	Dependant on the policy type. For a density-based policy, this value is the product of the maximum KBPS and the size of the attached snapshot. This is a read-only attribute.
Remote system	Comma-separated list of remote systems which the snapshot is replicated or will be replicated to. There are at most 4 remote systems.
Read/write hosts	Comma-separated list of identifiers of hosts allowed writing data. Applies only if the snapshot is attached to a dynamic snapshot mount point.
Read-only hosts	Comma-separated list of identifiers of hosts allowed reading data. Applies only if the snapshot is attached to a dynamic snapshot mount point.
Replicated	Indicates whether the snapshot is asynchronously replicated. Valid values: no—Not marked for replication pending—Marked for replication, but waiting synchronization yes—Successfully replicated to destination failed to replicate, check System Alerts for details—Failed to replicate in progress—snapshot is being transferred
Sync replicated	Indicates whether the snapshot participates in a synchronous replication session. Valid values: no—Either the snapshot was created on the destination site and will not be replicated on the source, or the snapshot was created before a synchronous replication session was set up. yes—Successfully replicated. failed to replicate—Snapshot was created on the source site while a replication session was in a fractured state. The snapshot was not replicated to the destination site.
Remote expiration time	Comma-separated list of expiration time corresponding to each remote system when the snapshot will be removed from each destination.
Remote allow auto-delete	Indicates whether this snapshot participates in auto-delete on the destination. Valid values are: yes no Default value is no.
Clone count	Indicates the number of thin clones associated with the snapshot.
Replication Origin	Array from which the replicated snapshot was created. Valid values: N/A — Indicates that the snapshot is not replicated to the remote system or it was synchronously replicated from the system whose OE version is older than 5.1.0. [System serial number] — Indicates the system where the snapshot originates from.

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Dell Unity™ Family Unisphere® Command Line Interface User Guide

Manage snapshots

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