Dell™ Storage Solutions Guide for
Microsoft® Hyper-V™
w w w . d e l l . c o m | s u p p o r t . d e l l . c o m

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Notes and Cautions
NOTE: A NOTE indicates important information that helps you make better use of
your computer.
CAUTION: A CAUTION indicates potential damage to hardware or loss of data if
instructions are not followed.
____________________
Information in this document is subject to change without notice.
© 2008 Dell Inc. All rights reserved.
Reproduction of these materials in any manner whatsoever without the written permission of Dell Inc.
is strictly forbidden.
Trademarks used in this text: Dell, the DELL logo, PowerVault, EqualLogic, and CLARiiON are
trademarks of Dell Inc.; Microsoft, Windows, Windows Server, Windows XP, MS-DOS, Hyper-V, and
Windows Vista are either trademarks or registered trademarks of Microsoft Corporation in the United
States and/or other countries; EMC is the registered trademark of EMC Corporation; SUSE Linux
Enterprise Server is a trademark of Novell, Inc. The abbreviation "SLES" is not a Novell trademark
but is used here due to space constraints.
Other trademarks and trade names may be used in this document to refer to either the entities claiming
the marks and names or their products. Dell Inc. disclaims any proprietary interest in trademarks and
trade names other than its own.
September 2008
Rev. A00

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Contents
Getting Started With Microsoft® Hyper-V™ Technology . 5
Understanding Hyper-V Architecture . . . . . . . . . . . 5
iSCSI Connections Within the Guest OS . . . . . . . 7
Storage Options for Virtual Machines (VMs) in Hyper-V . 7
Disk Type . . . . . . . . . . . . . . . . . . . . . . . 8
Disk Location . . . . . . . . . . . . . . . . . . . . 11
Disk Interface . . . . . . . . . . . . . . . . . . . . 13
Understanding the Storage I/O Path . . . . . . . . 15
Dell Supported Storage Arrays . . . . . . . . . . . . . 17
iSCSI Arrays. . . . . . . . . . . . . . . . . . . . . 18
Fibre Channel Arrays . . . . . . . . . . . . . . . . 25
SAS Arrays . . . . . . . . . . . . . . . . . . . . . 27
Additional Dell Supported Storage Solutions. . . . . . 30
Internal Storage . . . . . . . . . . . . . . . . . . 30
Host-Based RAID With External Enclosures . . . . 30
Sizing Storage for Your VM . . . . . . . . . . . . . . . 30
Sizing for VHDs . . . . . . . . . . . . . . . . . . . 32
Sizing for Passthrough Disks . . . . . . . . . . . . 33
Direct iSCSI Connectivity Within Guest OS . . . . . . . 34
iSCSI Connections from Both the Parent Partition and Guest OS
34
Direct iSCSI Connection Storage I/O Path . . . . . 35
iSCSI Connection Summary . . . . . . . . . . . . 36
Contents
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Appendix A: Planning for iSCSI-Based Storage Area Networks (SAN)
38
Physical Server Hosting Hyper-V . . . . . . . . . . 38
iSCSI Network Switches . . . . . . . . . . . . . . 38
Appendix B: Preparing Storage for Your VMs . . . . . . 40
Preparing the Disk for Use as a Passthrough Disk . 40
Preparing the Disk for Storing VHDs or VM Files. . 41
Appendix C: Glossary . . . . . . . . . . . . . . . . . . 42
Appendix D: References . . . . . . . . . . . . . . . . . 43
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Contents

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Getting Started With Microsoft® Hyper-V™
Technology
The Dell Storage Solutions Guide for Microsoft Hyper-V provides an
overview of:
•
Storage options available in Hyper-V
•
How Dell-supported storage solutions fit into a Hyper-V Deployment
•
Best practices associated with solution deployment
The solutions guidance provided in this guide is primarily focused on storage
arrays based on their support for key virtualization features, such as high
availability and virtual machine migration.
The information in this document assumes that you are familiar with the
basic concepts of Hyper-V (refer to Dell Solutions Overview Guide for
Microsoft Hyper-V at www.dell.com/hyper-v).
For additional information, see Dell Networking Solutions Guide for Microsoft
Hyper-V and Dell High Availability Solutions Guide for Microsoft Hyper-V at
www.dell.com/hyper-v.
Understanding Hyper-V Architecture
As described the Dell Solutions Overview Guide for Microsoft Hyper-V, the
parent partition (not the hypervisor) manages the I/O devices. To provide
virtual machines with access to those devices, Hyper-V supports a high-speed
interconnect referred to as the VMBus. Virtual devices, such as network and
storage adapters, for each VM communicate with the parent partition
through the VMBus. The parent partition receives those requests (through
the VSPs) and directs them to the underlying physical devices via the I/O
stack of the parent partition (refer to Figure 1). This model requires device
drivers for the physical devices to be installed in the parent partition.
NOTE: It is recommended that you download the latest Dell certified drivers
available for your system and install them in the parent partition. Using the latest
drivers ensures that both the parent partition and VMs are able to fully utilize the
underlying physical devices. Download the latest device drivers at
support.dell.com.
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Figure 1.
Hyper-V Architectural Overview
Guest operating systems requires specialized drivers (VSCs) provided by
Microsoft in order to access the VMBus. The drivers are specific to the type of
device that is presented to the guest operating system through the VM
configuration and are installed as a part of the Integration Services that are
available for Hyper-V supported guest operating systems.
NOTE: All architecture related information provided in this guide assumes that the
guest OS has Integration Services installed.
Advantages of Hyper-V device management model include the following:
•
Device specific drivers and utilities created for Windows Server 2008 x64,
work and do not require any changes when Hyper-V is enabled.
•
The configuration steps required for connectivity to a storage device in the
physical instance of Windows Server 2008 (Hyper-V is not enabled) are
identical when Hyper-V is enabled and those configuration steps should be
carried out in the parent partition.
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iSCSI Connections Within the Guest OS
Hyper-V supports iSCSI connections initiated directly from within a guest
operating system to an iSCSI storage array. In this configuration, an iSCSI
software initiator within the guest OS is connected to an iSCSI storage array.
The iSCSI connection and any iSCSI LUNs that are provisioned directly to
the guest OS are not visible by the parent partition. The parent partition’s
involvement is in the management of the networking devices and therefore is
not the primary focus of this document. For more information, see "Direct
iSCSI Connectivity Within Guest OS" on page 34.
Storage Options for Virtual Machines (VMs) in
Hyper-V
NOTE: The figures in this section do not represent best practices and are only
meant to depict possible configurations available with Hyper-V.
There are three major categories that must be considered for each disk that
will be presented to a VM. The options within each of the categories have a
unique set of attributes that determine critical factors such as compatibility,
performance, and availability:
D ISK TYPE — The type of disk the VM utilizes.
•
Virtual hard disk (VHD)
•
Passthrough disk
D ISK L OCATION — The physical location where the disk will be housed.
•
Internal storage
•
External storage
•
SMB/CIFS share
D ISK I NTERFACE — Based on the type of virtual controller the disk is attached
to, the disk will be presented to the VM as the desired disk interface.
•
IDE
•
SCSI
Storage Solutions Guide
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Disk Type
Virtual Hard Disk
A VHD is a file that resides on a formatted partition that the parent partition
has access to (see Figure 2). When presented to a VM, this file appears to the
guest OS as a hard disk with a set of raw blocks. The guest OS can utilize the
VHD just as it would a physical disk.
Figure 2.
VMs Using VHD
Three types of VHDs (defined at VHD creation) are supported:
D YNAMICALLY EXPANDING — The VHD file grows as data is stored to the disk
with a maximum size not exceeding the size specified during creation.
Dynamically expanding is the default option when creating a new virtual
machine using the New Virtual Machine Wizard in Hyper-V Manager.
F IXED SIZE — The VHD file uses the full amount of space specified during
creation.
D IFFERENCING — The VHD file exists as a child disk in a parent/child
relationship with an existing VHD. The parent VHD is left intact and changes
that occur are stored on the child (differencing) VHD.
NOTE: For production environments, a fixed-size VHD is recommended based on
increased performance over dynamically-expanding and differencing disks.
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Storage Solutions Guide

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Passthrough Disk
A passthrough disk is a physical disk mapped directly to a VM (see Figure 3).
To the parent partition, the disk is an offline state and direct read/write access
to the disk is not available. I/O requests from the VM are passed through the
parent partition to the disk. With the parent partition free from managing the
disk, additional CPU cycles are provided for virtual machine processing.
When mapped to a passthrough disk, the guest OS has direct access to the
raw blocks of the physical storage device.
Figure 3.
VMs Using Passthrough Disk
Considerations When Utilizing Passthrough Disks
•
Hyper-V does not restrict multiple VMs from selecting the same
passthrough disk during VM configuration. If the same passthrough disk is
selected by multiple VMs, data may be inadvertently overwritten. Ensure
that you select the appropriate disk during configuration.
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•
Hyper-V does not restrict VMs from selecting disks that have been made a
clustered resource as a passthrough disk. If disks that have been made a
clustered resource are selected as passthrough disks for other VMs, data
may be inadvertently overwritten. Ensure that you select the appropriate
disk during configuration.
•
A disk that is selected as a passthrough disk for a VM remains in the offline
state in the parent partition; however, if the disk is accidentally placed in
the online state, data corruption/loss may occur.
Disk Type Summary
Table 1.
Disk Type Summary
Disk Type
Advantages
Disadvantages
VHD
• Hyper-V VSS Support for host- • VHD size is limited to less
based backup of VMs
than 2 TB
• Greater portability - exported • Additional processor resources
VM can be easily
are required to manage I/O
copied/moved to another
requests to the VHD
location
• Multiple VHDs may reside on
a single physical disk
• Supports VM checkpoints
Passthrough
• Supports greater than 2-TB
• Does not support Hyper-V VSS
LUNs
for host-based backup of VMs
• Offers slightly higher
• Does not support Hyper-V VM
performance than VHDs
checkpoints
• Lacks portability of VHD (no
export)
• If booting from a passthrough
disk, an additional storage
location is required for the VM
files (XML, BIN, VSV)
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Storage Solutions Guide

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Document Outline

• Contents
  • Getting Started With Microsoft® Hyper-V’ Technology
  • Understanding Hyper-V Architecture
    • iSCSI Connections Within the Guest OS
  • Storage Options for Virtual Machines (VMs) in Hyper-V
    • Disk Type
    • Disk Location
    • Disk Interface
    • Understanding the Storage I/O Path
  • Dell Supported Storage Arrays
    • iSCSI Arrays
    • Fibre Channel Arrays
    • SAS Arrays
  • Additional Dell Supported Storage Solutions
    • Internal Storage
    • Host-Based RAID With External Enclosures
  • Sizing Storage for Your VM
    • Sizing for VHDs
    • Sizing for Passthrough Disks
  • Direct iSCSI Connectivity Within Guest OS
    • iSCSI Connections from Both the Parent Partition and Guest OS
    • Direct iSCSI Connection Storage I/O Path
    • iSCSI Connection Summary
  • Appendix A: Planning for iSCSI-Based Storage Area Networks (SAN)
    • Physical Server Hosting Hyper-V
    • iSCSI Network Switches
  • Appendix B: Preparing Storage for Your VMs
    • Preparing the Disk for Use as a Passthrough Disk
    • Preparing the Disk for Storing VHDs or VM Files
  • Appendix C: Glossary
  • Appendix D: References

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