emc vnx snapshots white paper

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  • 1 EMC VNX Snapshots White Paper

    White Paper

    Abstract

    This white paper describes EMC VNX Snapshots. The paper reviews and explains operations and best practices for the feature, as well as limits and functions.

    March 2015

    EMC VNX Snapshots

  • 2 EMC VNX Snapshots White Paper

    Copyright 2015 EMC Corporation. All Rights Reserved. EMC believes the information in this publication is accurate as of its publication date. The information is subject to change without notice. The information in this publication is provided as is. EMC Corporation makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose. Use, copying, and distribution of any EMC software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com. Part Number H10858.3

  • 3 EMC VNX Snapshots White Paper

    Table of Contents

    Executive summary .............................................................................. 5

    Audience ............................................................................................. 5

    Terminology ........................................................................................ 6

    VNX Snapshots Technical Overview ...................................................... 7 How Snapshots work ................................................................................... 7

    Snapshot granularity ............................................................................... 9 Snapshot Mount Point ............................................................................... 10

    VNX operations .................................................................................. 11 Create a Snap ............................................................................................ 11 Create a Snap with AppSync ...................................................................... 13 Create a Snapshot Mount Point ................................................................. 13 Attach a Snapshot ..................................................................................... 15 Branching (snap of a snap) ........................................................................ 15

    Copy a Snapshot ................................................................................... 16 Snap of a Snapshot Mount Point ........................................................... 17 Detach a Snapshot Mount Point ............................................................ 19 Detach a Snapshot Mount Point with Snapshots ................................... 20

    Destroy a Snapshot ................................................................................... 22 Consistency Groups................................................................................... 23

    Attach a Consistent Snapshot ............................................................... 25 Branch a Consistent Snapshot .............................................................. 28 Rules for Consistency Groups ................................................................ 29

    Restore ...................................................................................................... 29 Restore with SnapView Snapshots and VNX Snapshots ......................... 30 Restore a LUN ........................................................................................ 31 Restore CGs ........................................................................................... 33

    Repurpose Snapshots ............................................................................... 33 Migrations ................................................................................................. 33

    Migration considerations ...................................................................... 37 Limits ........................................................................................................ 37 Interoperability with other VNX features .................................................... 37

    VNX Snapshot Auto-Delete ................................................................. 38 Auto-Delete Thresholds ............................................................................. 40 Pool Space Used Threshold ....................................................................... 40

    Snapshot Space Used Threshold ........................................................... 41

  • 4 EMC VNX Snapshots White Paper

    Delete Eligibility ........................................................................................ 41 Auto-Delete paused ................................................................................... 42 Snapshot Expiration .................................................................................. 42

    CLI .................................................................................................... 43 Create a Snapshot ..................................................................................... 44 Copy a Snapshot ....................................................................................... 44 Create a Snapshot Mount Point ................................................................. 45 Attach a Snapshot ..................................................................................... 46 Create a Cascading Snapshot .................................................................... 46 Detach a Snapshot .................................................................................... 47 Destroy a Snapshot ................................................................................... 47 List all VNX Snapshots for a LUN ................................................................ 47 Create a Consistency Group ....................................................................... 48 List Consistency Groups ............................................................................ 48 Create a Consistent Snapshot ................................................................... 49 Attach a Consistent Snapshot ................................................................... 49

    SnapCLI............................................................................................. 49 Flush buffers ............................................................................................. 50 Create a Snapshot ..................................................................................... 50 Attach a Snapshot ..................................................................................... 50 Copy a Snap .............................................................................................. 50 Consistency Groups................................................................................... 50 Sample SnapCLI batch script ..................................................................... 51

    VNX Snapshots vs. SnapView terms ................................................... 52

    Properties Detailed ............................................................................ 53 Snapshot properties .................................................................................. 53 Snapshot Mount Point properties .............................................................. 54 Additional pool properties ......................................................................... 56

  • 5 EMC VNX Snapshots White Paper

    Executive summary VNX Snapshots is a VNX software feature that creates point-in-time data copies. VNX Snapshots is used for data backups, software development and testing, repurposing, data validation, and local rapid restores. Unlike SnapView snapshots and clones, VNX Snapshots do not consume large amounts of pool capacity. As a result, this feature is preferred for modern data management.

    This white paper describes all VNX Snapshots operations in detail. Wherever possible, all aspects of the feature sets are presented visually. The paper provides straightforward instructions for common functional tasks. Most tasks are shown from the point of view of Unisphere graphical user interface (GUI) and naviseccli command line interface (CLI). You can also manage your VNX snapshots using EMC AppSync, software that provides application consistent snapshots for Microsoft Exchange and SQL Server, and provides crash-consistency for VMware VMFS datastores. The AppSync GUI allows you to manage, configure, catalogue, and schedule your VNX snapshots.

    VNX Snapshots and SnapView will coexist on the same LUN. Furthermore, SnapView clones, which use a different technology from SnapView snapshots, will work with VNX Snapshots.

    Audience This paper is intended for EMC customers and EMC field personnel who are familiar with VNX technology. The paper is intended to be used as a main reference for VNX Snapshots technology.

  • 6 EMC VNX Snapshots White Paper

    Terminology Consistency Groupan object that contains a list of primary

    LUNs or Snapshot Mount Points (but not both) that are treated as a single entity for taking snapshots.

    Consistent Snapshota point-in-time copy of a Consistency Group.

    Copy on First Write (COFW)the technology behind SnapView Snapshots. After a snapshot is taken, new writes to the primary LUNs are delayed to enable copying old blocks to the special reserve LUN within the Reserve LUN Pool.

    Logical Unit Number (LUN)is the identifying number of a SCSI or an iSCSI object that processes SCSI commands. The LUN is the last part of the SCSI address for a SCSI object. The LUN is an ID for th

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