XenServerStorageOverview1

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Overview of XenServer Storage

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Objectives

Introduce basic types of storage used on XenServer.Identify each storage type.Describe how each storage type is accessed by XenServer.

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Summary

This training describes the type of storage available:LocalNetworkFiber


Why use storage?

Storage for XenServer is required to create a storage repository (SR) for the repository of virtual machine (VM) disks called VDIs.XenServer SR Storage Attributes are:

SR Storage can be local.SR Storage can be on another server.SR Storage can be on a SAN.

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Storage Repositories are Volumes Groups

Physical Volumes (PV1 + PV2 + PV3) create a Volume Group (VG1)Volume Group contains Logical Volumes You create a SR on a Volume Group

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Storage Repositories have a Physical Block Device (PBD)

A Physical Block Device (PBD) contains configuration from XenServer to SR.A virtual block device (VBD) is configuration of VDI to VM.Both PBD and VBDs are configurations only and can be recreated.


There are seven common storage types:

1- Local LVM 2- Local EXT 3- iSCSI4- NFS5- LVHD 6- Fiber Channel (FC)7- Connector (Dell EqualLogic and NetApp)

New!

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Type 1 is Local LVM

It is default when installing XenServer on local disk.Is logical volume format (LVM).VDIs stored as logical volumes.Max size of a VDI is 2TB.Can be spanned across multiple disks (Not Recommended)Note: Default local disk is formatted with 4GB partition for XenServer Dom0, 4GB partition for backups and upgrades, and remaining space for local SR.

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An example of LVM on Local Disk

Primary (4GB)/dev/sda1

Disk Internal

Primary Disk Partitioned

Backup (4GB)/dev/sda2

SR(#GB)/dev/sda3

LVM

/dev/sda

Note: LVM stands for Logical Volume Manager


Connectivity Requirements for local LVM are:

Having a local disk or LUN presented to a XenServer machine.Disk or LUN available via SCSI bus.You can see LVM disks with fdisk –l command.

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Type 2 is Local EXT (Extended File System)

The EXT type is a Linux EXT formatted file system.It has a similar file system structure like NFS.Virtual Machine VDIs are stored as files.Advantage is VDIs can be backed up like files.

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An example of EXT type on a Local Disk


Disk Internal



SR(#GB)/dev/sda3

EXT

/dev/sda


Connectivity Requirements for EXT are:

Having a local disk or LUN presented to a XenServer machine.Disk or LUN available via SCSI bus.You are required to manually format disk to be EXT when you create the an SR.Advantage of EXT is that it supports thin provisioning.

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Type 3 is iSCSI

iSCSI stands for (Internet Small Computer System Interface)Typical on Network Attached Storage (NAS) device.Carries SCSI commands over IP networks.Transmits data over local area networks (LANs).Less expensive than fiber channel.Supports multi-pathing.Currently iSCSI runs at 1GB/s speed.

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Software iSCSI is built into XenServer.It uses a software initiator.The software processing of iSCSI over TCP/IP data is handled in XenServer software and is much slower.Gig Ethernet networks have a half-duplex rate of 115 MB/s.

Hardware iSCSI has to be added with hardware device.Hardware device is called a HBA.Hardware has better performance due SCSI over TCP/IP offloading done on hardware.

iSCSI comes in Two Types: Hardware and Software


Dedicating a NIC for storage on XenServer.Assign an IP to NIC separate from management for iSCSI traffic.XenServer storage NIC and iSCSI NAS on same network.Generating an IQN (iSCSI Qualified Name) on XenServer.Enabling iSCSI software initiator on XenServer.

Software iSCSI Connectivity Requirements are:

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Installing iSCSI HBA (Host Bus Adapter) on XenServer.Configuring iSCSI HBA to target.Configure target with LUN to present to XenServer.A iSCSI target controller on SAN.

Hardware iSCSI Connectivity Requirements are:

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An example of iSCSI Software Type

Netw ork Switch

NIC Adapter

C itr ixXenServer

SAN

XenSever Server

iSC SI Target

Note: For Hardware iSCSI the NIC will be an HBA.


Type 4 is NFS Type

NFS stands for Network File SystemMust be formatted NFS Version 3. File system is mounted.It is accessed through network.Supports thin provisioning.Advantage is VDIs are stored as files.Downfall is VDI disk size cannot be increased.You can see location of NFS SR with mount command.

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Connectivity Requirements for NFS are:

Dedicate a NIC for storage on XenServer.Assign an IP to NIC separate from management for NFS traffic.XenServer storage NIC and NFS NAS must be on same network.Configure a Share on the NFS Server.Properly configure permissions to access share.

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A Type 4 NFS Sample Setup

NFS File System

XenServer

TCP/IP Network

Share


Type 5 is LVHD or VHD on LVM

It is new format for XenServer 5.5.It is intended to replace LVM as the default local SR type.Supports snapshots.Hosts VHD files directly on LVM volumes.LVHD supports two VDI formats: Raw volumes and VHD volumes.VHD is the default VDI format for LVHD SRs.VHD VDIs are LVM volumes formatted with VHD metadata

New!

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Connectivity Requirements for LVHD are:

LVHD SRs can reside on local, network or fiber disks.Disk will have to be upgraded or formatted LVHD.You can use the command /opt/xensource/bin/xe-lvm-upgrade <SR UUID> to upgrade disk.

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A Type 5 LVHD Sample Setup on Local Disk


Disk Internal



SR(#GB)/dev/sda3

LVHD

/dev/sda

Note: LVHD can be installed on local, iSCSI, or FC storage.


Type 6 is Fiber Channel (FC)

Natively LVM format.Accessed through a Fiber Channel HBA.Supports multi-pathing.Currently runs at 2 GB/s.A properly configured 2GB/s Fiber Channel SAN is capable of sustaining in excess of 380MB/sec speed.Fiber Channel is more reliable than iSCSI storage.

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Connectivity Requirements for FC

Install a Hardware HBA on the XenServer (Two or more for Multi-Pathing)Configure SAN with LUN to present to HBA.Connect Fiber Channel Optic Cables.Configure FC Switch with appropriate Zoning.

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A FC Sample Setup

F i b e r C h a n n e l S w i t c h e s

H o s t B u s A d a p t e r s ( H B A s )

C i t r i xX e n S e r v e r s

S A N

X e n S e v e r S e r v e r X e n S e v e r S e r v e r

F C S A N

( L o c a l D i s k P r e s e n t a t i o n ) ( L o c a l D i s k P r e s e n t a t i o n )


Type 7 is Connector Type

The two connectors available are the Dell Equal Logic and the NetApp plug-in.Connectors are specific for third party vendors.Uses software iSCSI for connectivity.Alleviates administrative access to backend.Support backend snapshots.

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Connectivity Requirements for Type 7 are:

Dedicating a NIC for storage on XenServer.Assign an IP to NIC separate from management .XenServer storage NIC and iSCSI NAS must be on same network.Administrative access to the backend is necessary.

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Additional NetApp Plug-in Requirements are:

ONTAP 7G version.7.0 or greater can be used as custom SR.

XenServer supports the following NetApp features:Thick ProvisioningThin ProvisioningA-SIS data de-duplicationSnapshotting that uses FlexVol technology


Example of XenServer Storage GUI:

XenServerStorageOverview1

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