Technical Support Group
Bangalore
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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
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Manageability
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You can manage all storages using an intuitive graphical user interface
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Provides consistent management across all the platforms ( Solaris, HPUX, Windows NT/2000, IBM)
Management of storage is performed on-line in real time , eliminating
the need for downtime.
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Benefits of Volume Manager
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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 protects
Against multiple simultaneous disk failures
Recovery Time is minimized, through logging and background mirror
Synchronization.
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Benefits of Volume Manager
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Performance
I/O Throughput is maximized by measuring and modifying volumes
Layouts while storage remains on-line.
Performance bottlenecks can be eliminated using the VxVm analysis
tool.
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Benefits of Volume Manager
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Scalability
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VxVM Runs on both 32 But and 64 Bit Operating systems
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Storage can be deported to large enterprise-class platforms
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Storage devices can be spanned
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VxVM is fully integrated with Veritas File System
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Veritas Volume Manager Fundamentals
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
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Physical Storage Objects
VTOC: Stores Information about Disk structure and Organization. Also Called as Disk Label
Partition: After VTOC, remainder of the Disks are divided ito units called Partitions
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How Does Volume Manager Works
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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.
Technical Support Group
Bangalore
9
What Happens to a Disk under VxVM Control
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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
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Disk Groups
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Volume Manager Disks
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Sub-Disks
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Plex
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Volume
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Virtual Objects
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Volume Manager consists of variety of virtual objects .Volume is one of
the variety of the virtual Objects.
Technical Support Group
Bangalore
12
Disk Group
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Disk group is a collection of VxVM disks. You group disks into disk
groups for management purpose.
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Volume Manager Disks
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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.
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Bangalore
14
Sub Disks
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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.
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15
Plex
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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.
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Bangalore
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Volumes
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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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Bangalore
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Summary Of Virtual Objects
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Volume Layouts
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Volume layout refers to organization of plexes in a volume.
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Concatenated Volume
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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
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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
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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
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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
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Which Disks Under VxVM control
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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.
Technical Support Group
Bangalore
25
Enclosure based Naming
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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
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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
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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.
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Preserve or eliminate disk data
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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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Bangalore
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System Root Disk under VxVM Control
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Typical Initial VxVM Setup
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Bangalore
31
Volume Manager Installation
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Software Packages
VRTSvxvm
VRTSlic
VRTSvmdev
VRTSvmman
VRTSvmdoc
VRTSvmsa
Drivers and Utilities
Licensing Utilities
Developer Kit
Manual Pages
Documentation
Storage Administration Server and Client
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The vxinstall Program
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This program is used to initialize the volume manager after adding the
software package.
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Should be run only once in a System
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Purpose of this program is to create rootdg disk group
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Volume Manager requires rootdg disk group and it should contain at
least one disk
This program is an interactive tool.
Example : # vxinstall
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The vxinstall program
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34
Volume Manager User Interface
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Volume Manager Storage Administrator (VMSA- Gui)
Ex: # vmsa &
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or
# vea &
Command Line Interface
Ex: # vxdg list
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Volume Manager Support Operations (Menu Driven)
Ex: # vxdiskadm
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VMSA Main Window
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36
Command Line Interface
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Many of the commands can be found in
/etc/vx/bin
/usr/sbin
/usr/lib/vxvm/bin
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Examples :
# vxdisk list
# vxdg list
# vxprint -ht
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Vxdiskadm Interface
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38
Adding Disks
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Before You Add Disks.
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Disk Configuration Stages
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Prior-VxVM
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Disk Configuration Steps
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Stage One
An Initialized Disk is placed under Volume Manager’s Free Disk pool.
While initializing it will create private and public region.
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Bangalore
41
Disk Configuration Steps
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Stage Two
An initialized Disk is placed under Disk Group.Disk Media Name is
assigned to it.
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42
Disk Configuration Steps
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Stage Three
Creating Volumes . Assigning disk space to volumes.
Technical Support Group
Bangalore
43
Adding Disk : CLI
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The vxdisksetup Command:
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# vxdisksetup –i c1t0d0
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# vxdg –g oradg adddisk c1t0d0=disk01
[ Initialize Disk ]
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.
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Viewing Disk Information
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45
Viewing Disk Information
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Information on individual disk.
# vxdisk list <diskname>
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Removing a Disk.
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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
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# 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
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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.
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Managing Disk group
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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
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50
Managing Disk Group
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Example of Re-configuration
Run # vxdctl enable
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Managing Disk group
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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.
Technical Support Group
Bangalore
52
Managing Disk group
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Disk group and High Availability
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Creating Disk Group (CLI)
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To create a disk group from command line use the following command
# vxdg init newdg newdg01=c1t1d0s2
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To verify whether disk group is created
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Setting up Spare Disk
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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
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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 group
Example:
# umount /data
# umount /data1
# vxdg deport datadg
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Making Disk Groups Available
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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
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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
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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
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Viewing DiskGroup Information
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Vxdisk and vxdg commands
Example:
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61
Viewing DiskGroup Information
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Example:
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Viewing DiskGroup Information
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Viewing Free Space
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Working With Volumes
What is Volume & Volume layout ?
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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
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RAID 0
- Simple Concatenation or striping
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RAID 1
- Mirroring
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RAID 5
- Striping with distributed parity.
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RAID 0+1
- Adding Mirror to a concatenated / striped layout
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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)
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The “vxassist” Utility
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Syntax: vxassist –g <diskgroup> make <volname> length [attributes]
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#
#
#
#
#
vxassist
vxassist
vxassist
vxassist
vxassist
–g
–g
–g
–g
–g
datadg
datadg
datadg
datadg
datadg
make
make
make
make
make
vol1
vol1
vol1
vol1
vol1
50m
50m datadg01
500m layout=stripe
500m layout=stripe stripeunit=64k
200m layout=mirror disk01 disk02
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Estimating Volume Size
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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=raid5
The above command estimates the maximum size of an raid5 volume
that can be created.
# vxassist –g datadg maxgrow datavol
The above command estimates how much the volume (datavol) can be
growed.
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Viewing Volume Information
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Use # vxprint , for volume information
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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)
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Syntax : vxassist –g <diskgroup> remove volume <volname>
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Example One.
# vxassist –g oradg remove volume oravol1
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Example Two.
# vxedit –rf rm oravol
The above command will complete remove all the underlying plexes
and subdisks of the volume “oravol”
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Adding a Mirror Volume
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Syntax : vxassist –g <diskgroup> mirror <volume name>
Example:
# vxassist –g oradg mirror oracle
The above command mirrors the oracle volume
# vxassist –g oradg mirror oracle oradg01
The above command mirrors oracle volume on to the disk oradg01
# vxmirror –g oradg –a
The above command mirrors all the unmirrored volumes in oradg
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Removing a Mirror
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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
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Two Types of logging are supported in VxVM:
Dirty Region Logging for mirrored volumes
RAID-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)
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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
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