IBM Storwize V5020 User Manual

496 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
10.3.4 FlashCopy indirection layer
The FlashCopy indirection layer governs the I/O to the source and target volumes when a
FlashCopy mapping is started, which is done by using a FlashCopy bitmap. The purpose of
the FlashCopy indirection layer is to enable the source and target volumes for read and write
I/O immediately after the FlashCopy is started.
To show how the FlashCopy indirection layer works, we examine what happens when a
FlashCopy mapping is prepared and then started.
When a FlashCopy mapping is prepared and started, the following sequence is applied:
1. Flush the write cache to the source volume or volumes that are part of a Consistency
Group.
2. Put cache into write-through mode on the source volumes.
3. Discard cache for the target volumes.
4. Establish a sync point on all of the source volumes in the Consistency Group (which
creates the FlashCopy bitmap).
5. Ensure that the indirection layer governs all of the I/O to the source volumes and target
volumes.
6. Enable cache on the source volumes and target volumes.
FlashCopy provides the semantics of a point-in-time copy by using the indirection layer, which
intercepts I/O that is directed at the source or target volumes. The act of starting a FlashCopy
mapping causes this indirection layer to become active in the I/O path, which occurs
automatically across all FlashCopy mappings in the Consistency Group.
The indirection layer then determines how each I/O is to be routed, based on the following
factors:
򐂰 The volume and the logical block address (LBA) to which the I/O is addressed
򐂰 Its direction (read or write)
򐂰 The state of an internal data structure, the FlashCopy bitmap
The indirection layer allows the I/O to go through to the underlying volume, redirects the I/O
from the target volume to the source volume, or queues the I/O while it arranges for data to be
copied from the source volume to the target volume. To explain in more detail which action is
applied for each I/O, we first look at the FlashCopy bitmap.
FlashCopy Consistency Groups
per system
255 This maximum is an arbitrary limit that is policed
by the software.
FlashCopy volume capacity per
I/O Group
4 pebibytes
(PiB)
This maximum is a limit on the quantity of
FlashCopy mappings that are using bitmap space
from this I/O Group. This maximum configuration
uses all 4 gibibytes (GiB) of bitmap space for the
I/O Group and allows no Metro or Global Mirror
bitmap space. The default is 40 tebibytes (TiB).
FlashCopy mappings per
Consistency Group
512 This limit is because of the time that is taken to
prepare a Consistency Group with many
mappings.
FlashCopy property Maximum Comment

IBM Storwize V5020 Specifications

General

Model	Storwize V5020
Category	Storage
Maximum Number of Drives	240
Form Factor	2U
Supported Protocols	iSCSI
Drive Types Supported	SSD, SAS, NL-SAS
Expansion Units	Up to 9
RAID Levels Supported	0, 1, 5, 6, 10
Host Interface	16 Gb FC, 10 Gb iSCSI
Interface Types	Fibre Channel, Ethernet, SAS
Power Supply	Dual redundant power supplies

Summary

Overview of the IBM Storwize V5000 Gen2 system

IBM Storwize V5000 Gen2 overview

Provides an overview of the Gen2 system, its models, and benefits.

IBM Storwize V5000 Gen2 models

Compares the features and specifications of different Storwize V5000 Gen2 models.

IBM Storwize V5000 Gen2 hardware

Describes the hardware components of the Storwize V5000 Gen2 solution.

Initial configuration

Hardware installation planning

Outlines requirements and checklist for planning hardware installation.

SAN configuration planning

Discusses planning for Fibre Channel SAN connectivity.

First-time setup

Guides through the initial setup process for a first-time IBM Storwize V5000 Gen2 service.

Initial configuration

Details how to complete the initial configuration, including component verification.

Storage pools

Working with internal drives

Describes configuring internal storage disk drives and actions on them.

Working with storage pools

Explains how storage pools are managed and created.

Working with managed disks

Details how to manage MDisks, including their modes and assignments.

Host configuration

Preparing the host operating system

Details steps to prepare Windows and VMware ESXi hosts for attachment.

Creating hosts by using the GUI

Guides on creating Fibre Channel, iSCSI, and SAS hosts.

Volume configuration

Creating volumes using the Volume Creation

Details creating basic, mirrored, custom, and HyperSwap volumes.

Mapping a volume to the host

Guides on mapping created volumes to hosts.

Storage migration

Storage migration wizard overview

Storage migration wizard

Details the steps involved in the storage migration wizard.

Advanced host and volume administration

Advanced host administration

Covers host modification, mappings, and deletion.

Advanced volume administration

Details volume modification and copy creation.

Advanced features for storage efficiency

Easy Tier

Describes the Easy Tier disk performance optimization function.

Thin provisioning

Real-time Compression software

Details the Real-time Compression software for storage efficiency.

Copy services

IBM FlashCopy

Describes the FlashCopy function for point-in-time copies.

Implementing FlashCopy

Remote Copy

Troubleshooting remote copy

HyperSwap

Explains HyperSwap functionality for high availability.

External storage virtualization

Planning for external storage virtualization

Describes planning steps for virtualizing external storage.

Working with external storage

RAS, monitoring, and troubleshooting

Reliability, availability, and serviceability features

Describes RAS features and monitoring.

Configuration backup

Explains how to back up system configuration.

System update

Describes updating node canister software and drive firmware.

Support Assistance

Describes local and remote support assistance.

Collecting support information

Details how to collect support data using GUI and CLI.

Powering off the system and shutting down the infrastructure

Encryption

Planning for encryption

Discusses planning for data-at-rest encryption.

Defining encryption of data at-rest

Activating encryption

Guides on activating encryption licenses.

Enabling encryption

Details enabling encryption using key servers or USB flash drives.

Rekeying an encryption-enabled system

CLI setup and SAN Boot

Command-line interface