What is Veritas Volume Manager

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What is Veritas Volume Manager

Veritas Volume Manager is an Online Storage Management Tool

that provide a logical volume management layer which overcomes

the physical restrictions of disk devices by spanning volumes across the

spindles. It protects against the Disk and Hardware failure

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Benefits of Volume Manager

Manageability

You can manage all storages using an intuitive graphical user interface

Provides consistent management across all the platforms ( Solaris, HP-UX, Windows NT/2000, IBM)

Management of storage is performed on-line in real time , eliminatingthe need for downtime.

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Availability

Integrity of storage is maintained by true mirroring across all writes

Through RAID Techniques, Storage remains available in the event of

Hardware failures Data Redundancy is maintained by hot-relocation, which

protectsAgainst multiple simultaneous disk failures

Recovery Time is minimized, through logging and background mirrorSynchronization.

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Performance

I/O Throughput is maximized by measuring and modifying volumesLayouts while storage remains on-line.

Performance bottlenecks can be eliminated using the VxVm analysis tool.

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Scalability

VxVM Runs on both 32 But and 64 Bit Operating systems

Storage can be deported to large enterprise-class platforms

Storage devices can be spanned

VxVM is fully integrated with Veritas File System

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Describe how physical data storage relates to virtual data storage in Veritas Volume Manager.

Install Veritas Volume Manager

Perform Volume Management Tasks Using GUI and CLI.

Manage Disks and Disk Groups

Create and Manage Virtual Volumes

Veritas Volume Manager Fundamentals

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Physical Storage Objects

VTOC: Stores Information about Disk structure and Organization. Also Called as Disk LabelPartition: After VTOC, remainder of the Disks are divided ito units called Partitions


How Does Volume Manager Works

You Enable Virtual data storage by bringing the disks under volume manager control.It means that volume manager creates virtual objects and establishes a logical connection between those objects and underlying physical objects.

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What Happens to a Disk under VxVM Control

Volume Manager removes all the partition table entry from VTOC

Creates two partitions on the physical disk. One is Private region and second is public region.

Private region stores information like configuration database,kernel logs, and disk headers.Minimum size is 1024 Sectors and Maximum is 512000 Sectors ( 512k Sectors)

Public Region consists of the remainder of the Disk.This represents the available space for VxVM to create volumes and assign data to it.

Volume Manager updates the VTOC, with information about the removal of the existing partition and the addition of the new partition during initialization process.

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Volume Manager-Virtual Objects

Disk Groups

Volume Manager Disks

Sub-Disks

Plex

Volume


Virtual Objects

Volume Manager consists of variety of virtual objects .Volume is one of the variety of the virtual Objects.

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Disk Group

Disk group is a collection of VxVM disks. You group disks into disk groups for management purpose.


Volume Manager Disks

A Volume Manager Disk is created as soon as a physical disk is brought under VxVM control.

Each VxVM disk corresponds to one physical Disk.


Sub Disks

A VxVM Disk can be divided into one or more sub-disks. A sub-disk is a set of contiguous blocks that represents a specific portion of VxVM disk, which is mapped to specific region of the Disk.


Plex

A Plex is a structured or ordered collection of sub-disks that represents a copy of data. A plex consists of one or more sub-disks located in one or more physical disks.


Volumes

A Volume is a virtual storage device that is used by applications in a manner similar to physical disk. Volume is composed of one or more plexes.

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Summary Of Virtual Objects

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Volume Layouts

Volume layout refers to organization of plexes in a volume.

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Concatenated Volume

In a concatenated volume, sub disks are arranged both sequentially and contiguously Concatenation allows a volume to be created from one or more physical disks, if there is not enough free space to accommodate the volume in a single disk

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Striped Volume

In a Striped Volume, data is spread evenly across the sub-disks. Stripes are equally sized fragments that are allocated alternately and evenly to the sub-disk inside a single plex. There must be at least two sub-disks inside a plex, each of which must exist on different physical disk

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Mirrored Volume

Mirrored Volume uses multiple plexes to duplicate the information contained in a volume. At least two plexes are required for a true mirroring.Each of this plexes must exists on different physical disk for redundancy.

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RAID-5 Volume

A RAID-5 Volume uses striping to spread data and parity evenly across physical disks. Each stripe consists of a parity stripe unit and data stripe unit.Parity can be used to re-construct the data if one disk fails

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Planning First time VxVM Setup


Which Disks Under VxVM control

The only disks that you should place under VxVM control during installation are the root disk and its mirror.

You can add other disks and disk groups after installation If you do not plan to bring the system disk under VxVM

control, then place one disk under rootdg.

Rootdg is required, so that volume manager daemons can be started in enabled mode.

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Enclosure based Naming

This allows VxVM to access enclosures as a separate physical entities.Enclosure based naming can be useful while implementing DMP(Dynamic Multipathing).When you install VxVM, You are prompted whether to use enclosure based naming

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Excluding Disks

If you want any disks to be excluded from volume manager control, then you can specify in the exclusion files

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Prevent Multi-pathing

With VxVM version 3.1.1 later, DMP Driver must always be present on the system for VxVM to function.However you can prevent VxVM from multipathing some or all devices without removing the DMP layer.


Preserve or eliminate disk data

When you place a disk under volume manager control, either you can preserve the data (Encapsulation) or eliminate the data (initialization)

Encapsulation should contain minimum 2 free partition table entries on the disk to be encapsulated.

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System Root Disk under VxVM Control


Typical Initial VxVM Setup

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Volume Manager Installation

Software Packages

VRTSvxvm Drivers and Utilities VRTSlic Licensing Utilities VRTSvmdev Developer Kit VRTSvmman Manual Pages VRTSvmdoc Documentation VRTSvmsa Storage Administration Server and Client

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The vxinstall Program

This program is used to initialize the volume manager after adding the software package.

Should be run only once in a System

Purpose of this program is to create rootdg disk group

Volume Manager requires rootdg disk group and it should contain at least one disk

This program is an interactive tool.

Example : # vxinstall


The vxinstall program

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Volume Manager User Interface

Volume Manager Storage Administrator (VMSA- Gui)

Ex: # vmsa & or # vea &

Command Line Interface

Ex: # vxdg list

Volume Manager Support Operations (Menu Driven)

Ex: # vxdiskadm


VMSA Main Window

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Command Line Interface

Many of the commands can be found in

/etc/vx/bin /usr/sbin /usr/lib/vxvm/bin

Examples :

# vxdisk list# vxdg list# vxprint -ht


Vxdiskadm Interface

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Adding Disks

Before You Add Disks.

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Disk Configuration Stages

Prior-VxVM


Disk Configuration Steps

Stage OneAn Initialized Disk is placed under Volume Manager’s Free Disk pool. While initializing it will create private and public region.



Stage TwoAn initialized Disk is placed under Disk Group.Disk Media Name is assigned to it.



Stage ThreeCreating Volumes . Assigning disk space to volumes.

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Adding Disk : CLI

The vxdisksetup Command:

# vxdisksetup –i c1t0d0 [ Initialize Disk ]

# vxdg –g oradg adddisk c1t0d0=disk01

The above command add the disk c1t0d0 to diskgroup “oradg” with disk name as disk01. When you add a disk to diskgroup, it is stamped with the system host id. Note: Diskgroup should exist.


Viewing Disk Information

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Viewing Disk Information

Information on individual disk. # vxdisk list <diskname>

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Removing a Disk.

Before removing a disk, make sure there is no data on the disk. Else you evacuate the data on the disk onto another disk.

Evacuating a Disk moves the content of the disk onto other disk.

The disk to which data is evacuated should belong to the same disk group.

Example:

# vxevac –g oradg disk01 disk02.

The above command evacuates data from disk01 to disk02 under diskgroup oradg

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Removing a Disk

# vxdg –g oradg rmdisk disk01

The above command removes the disk “disk01” from diskgroup “oradg” and places the disk in free disk pool.

Once the disk is placed in free pool, it can be completely taken out of volume manager control using the following command

# vxdiskunsetup –C c1t0d0

-C option forces the de-configuration

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Managing Disk Groups

Why Disk Groups ?

Disk Groups enables grouping of disks into logical collections for a particular set of users or applications.

It can be easily moved from one host machine to another. Enables high availability. This can be shared by two or more

hosts, but only one can access at a time. If one host crashes, other host takes over.

You can never have an empty disk group. Disk group cannot share resources. ( One disk belonging to

Multiple disk group.


Managing Disk group

Disk Media Name: Unique name assigned to a disk, when it is added to the disk group.

Disk Access record: Mapping of physical disk location to Disk media name. This record can be re-created by running # vxdctl enable


Managing Disk Group

Example of Re-configuration Run # vxdctl enable


Managing Disk group

rootdg The rootdg is a special disk group which is created during

vxinstall process. VxVM requires rootdg with atleast one disk, to start volume

manager. If you want your boot disk to be bootable under volume

manager, then boot disk must be in rootdg Rootdg follows different disk naming conventions than other

disk groups ( rootdg disk names: disk01, disk02, ….) Rootdg can not be destroyed or deleted.

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Managing Disk group

Disk group and High Availability

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Creating Disk Group (CLI)

To create a disk group from command line use the following command

# vxdg init newdg newdg01=c1t1d0s2

To verify whether disk group is created

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Setting up Spare Disk

Setting a spare disk inside a Disk group enables the hot-relocation feature of VxVM. If an I/O failure occurs, hot-relocation automatically relocates the redundant subdisks to the spare disk and restores the affected volume manager data and objects.

Example:

# vxedit –g oradg set spare=on oradg01

The above example sets disk “ oradg01” as a spare to the disk group “oradg”

Note: This is applicable only for RAID-1 and RAID-5 Volumes

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Making Disk group Un-available

Deporting a Disk Group makes the disk group and its volume unavailable. This means that disk group and its objects can not be accessed. To resume management it needs to be imported.

When you deport the disk group you also have the option to rename to the disk group.

You also have the option to specify the new host, to which disk group will be imported next time.

Before deporting you need to unmount all the file systems lying under disk groupExample:

# umount /data# umount /data1# vxdg deport datadg

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Making Disk Groups Available

Importing a disk group re-enables the access to a deported disk group.

To move a disk group from one system to another system, it needs to deported on first system and then imported on to other system

You can rename the disk group while importing. Importing a disk group

# vxdg import datadg

Importing and rename# vxdg –n newdg import datadg

Import and temporarily rename# vxdg –t –n newdg import datadg

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Disk group Host-Lock

When a disk group is created, system writes a lock on to the disk group header. This lock is nothing but the value in hostname field of the disk group header.

The lock ensure that, dual-ported disks are not used by both the systems at the same time. If a system crashes, the lock remains on the disk group and it prevents the other machine from being imported.If you are sure that the disk group is not in use by other system, then the host lock can be cleared while importing the disk group.

Example:

# vxdg –Cf import datadg

The above command clear the host lock and forces the import.

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Moving Disk Group

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Destroying Disk Group

Destroying a disk group permanently removed the disk group from volume manager, and places all the disks in free disk pool. Volume and configuration information are removed.

Example:

# vxdg destroy olddg


Viewing DiskGroup Information

Vxdisk and vxdg commands Example:

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Example:

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Viewing Free Space

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Working With Volumes

What is Volume & Volume layout ?

Volume is made up of portions of one or more physical disks. Volume can provide greater flexibility, availability, and

performance than a single physical disk. Volume layout is based on the way plexes are organized to

remap the volume address space through which I/O is redirected at run time.

Each volume layout has their own advantages and dis-advantages

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VxVM Supported RAID Levels

RAID 0 - Simple Concatenation or striping

RAID 1 - Mirroring

RAID 5 - Striping with distributed parity.

RAID 0+1 - Adding Mirror to a concatenated / striped layout

RAID 1+0 - Mirroring occurs below the concatenation / striping

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Concatenated Layouts

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Striped Layout

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Mirrored Layout

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RAID-5 Layout

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RAID 0+1 ( Mirror-Stripe)

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RAID 0+1 ( Mirror-Concat)

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Creating Volumes (CLI)

The “vxassist” Utility

Syntax: vxassist –g <diskgroup> make <volname> length [attributes]

# vxassist –g datadg make vol1 50m # vxassist –g datadg make vol1 50m datadg01 # vxassist –g datadg make vol1 500m layout=stripe # vxassist –g datadg make vol1 500m layout=stripe

stripeunit=64k # vxassist –g datadg make vol1 200m layout=mirror disk01

disk02

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Estimating Volume Size

Before Creating a volume in a diskgroup, its necessary to estimate the volume size that is going to get created.

Example :

# vxassist –g datadg maxsize layout=raid5The above command estimates the maximum size of an raid5 volume that can be created.

# vxassist –g datadg maxgrow datavolThe above command estimates how much the volume (datavol) can be growed.

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Viewing Volume Information

Use # vxprint , for volume information

Example:

# vxprint –rht# vxprint –g oradg –ht

Options:-r ---Display layered volume information-h ---List hierarchies below selected records-t ---Print single line output records

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Vxprint Example

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Removing a Volume (CLI)

Syntax : vxassist –g <diskgroup> remove volume <volname>

Example One.

# vxassist –g oradg remove volume oravol1

Example Two.

# vxedit –rf rm oravolThe above command will complete remove all the underlying plexes and subdisks of the volume “oravol”

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Adding a Mirror Volume

Syntax : vxassist –g <diskgroup> mirror <volume name>

Example:# vxassist –g oradg mirror oracleThe above command mirrors the oracle volume

# vxassist –g oradg mirror oracle oradg01The above command mirrors oracle volume on to the disk oradg01

# vxmirror –g oradg –aThe above command mirrors all the unmirrored volumes in oradg

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Removing a Mirror

For example for the volume “datavol”, to remove the plex that contains the sub disk from datadg01 disk, execute# vxassist –g datadg remove mirror datavol !datadg01

For example, to remove the plex that uses any disk except datadg01# vxassist –g datadg remove mirror datavol datadg01

Other methods:# vxedit –g datadg –rf rm datavol-02 Where datavol-02 is the plex name.

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Logging In VxVM

Two Types of logging are supported in VxVM:Dirty Region Logging for mirrored volumesRAID-5 logging for RAID-5 volumes

DRL: This is used with mirrored volumes. This keeps track of the regions that have changed due to I/O writes to the volumes.Prior to every write a bit-map is written to a log to record the area of the disk that is being changed. In case of a system failure, DRL uses this information to recover only the portions of the region that has changed.

RAID-5: When you create a RAID-5 volume, a RAID-5 log is created by default. This is used for speedy resync of the volume, in case of a system failure

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Adding a log (CLI)

You can add a log volume to only mirrored and RAID-5 Volumes

Example:To add a log to mirrored volume# vxassist –g datadg addlog datavol logtype=drl

Example:To add a log to RAID-5 volume# vxassist –g oradg addlog oracle

Note: VxVM automatically recognizes the RAID-5 Layout and add the log

Documents

What is Veritas Volume Manager