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LVM and VxVM an Introduction

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					 LVM and VxVM
  an Introduction


     By Bill Hassell
With acknowledgements to
    David Totsch and
       Chris Wong


                           1
LVM - Introduction


     LVM Basics
HFS and VxFS filesystem



                          2
                  LVM - Disk Layout
                        LIF Header      LVM Record

                      Physical Volume   Bad Block
Volume Group           Reserve Area     Directory
Descriptor Area
Volume Group
                        Boot Data        Duplicate
                                        Information
 Status Area           Reserve Area
   Mirror              Volume Group
 Consistency
  Records
                       Reserve Area
  Redundant             LIF Volume
 Information
                      Bad Block Pool
                         Physical
                         Extents
                                                      3
LVM Allocation
       Linear   Pvol 1

                  1

                  2

Lvol              3

 1                4

 2                5

 3                6

 4

 5              Pvol 2

 6                1

 7                2

 8                3

                  4

                  5

                  6      4
LVM Allocation
       Mirroring   Pvol 1

                     1

                     2

Lvol                 3

 1                   4

 2                   5

 3                   6

 4

 5                 Pvol 1

 6                   1

                     2

                     3

                     4

                     5

                     6
                            5
     LVM Allocation
         Striping   Pvol 1
                      1
                      2
                      3
                      4
Lvol
                      5
                      6
 1

                    Pvol 2
 2
                      1
                      2
 3
                      3
                      4
 4
                      5
                      6
 5

                    Pvol 3
 6
                      1
                      2
                      3
                      4
                      5
                      6


                             6
     LVM Allocation
       "Chunking"
             Pvol 1   Pvol 4
              1        1
              2        2
Lvol
              3        3
              4        4
 1
              5        5
              6        6
 2

             Pvol 2   Pvol 5
 3
              1        1
              2        2
 4
              3        3
              4        4
 5
              5        5
              6        6
 6

             Pvol 3   Pvol 6
              1        1
              2        2
              3        3
              4        4
              5        5
              6        6
                               7
 LVM Allocation
         fragmentation
before        interim     after

Pvol 1        Pvol 1     Pvol 1
lvol 1        lvol 1      lvol 1
lvol 1        lvol 1      lvol 1

lvol 2                   lvol 4-e
lvol 2                   lvol 4-f
lvol 2                   lvol 4-g
lvol 3        lvol 3      lvol 3

lvol 3        lvol 3      lvol 3
lvol 3        lvol 3      lvol 3

lvol 4        lvol 4     lvol 4-a
lvol 4        lvol 4     lvol 4-b

lvol 4        lvol 4     lvol 4-c
lvol 4        lvol 4     lvol 4-d

                                    8
           LVM Performance
• Mirroring
  – recovery policy
  – cache
• Extent Size
  – Is bigger really better?
• Number of Disks


                               9
            LVM Convenience
• Mirrors
  – Splitting
  – Merging
• vgexport/vgimport
• pvmove (!)



                              10
               LVM Don'ts
•   Span disks w/o mirroring
•   Leave /etc/lvmtab alone
•   vgscan is a last resort
•   backup w/o running vgcfgbackup




                                     11
           File System Types
•   UFS    a.k.a. HFS
•   VXFS   Veritas Journaled File System
•   CDFS   CD-ROM File System
•   NFS    Network File System




                                           12
                               Boot Block




                     DATA




        DATA
                               SuperBlock
                  Boot Block
     Boot Block                 INODES
                  SuperBlock
     SuperBlock
                   INODES
      INODES
                                  DATA




                     DATA
                                         HFS Layout On Disk




        DATA



13
     Fragmentation
O    3k
X    9k
Z    18k
O   O O X   Z   Z
Z   Z Z Z   Z   Z Z Z
X   X X X   X   X X X
Z   Z Z Z   Z   Z Z Z   14
                  Inode
   File Size
  File Type       •   Direct - 96KB File
    Mode
     UID
                  •   Single - 16.8MB
     GID          •   Double - 34GB
 Link Count
Time Stamps       •   Triple - 70TB
   12 Direct

Single Indirect   • 59 Char Fast SymLink
Double Indirect
Triple Indirect
                                           15
                       Directory
      Directory name     inode
.                         78       this inode
..                        22       parent directory
.profile                  128
resume                    101
junk                      0        "Empty Entry"
bin                       88       Directory?
myStuff                   269

                                                16
               How HFS Works
SB




     • Files stay in cylinder groups, where
       possible.
     • Flat performance until > 80% full.
     • Most accommodating to many small files.

                                                 17
          JFS (a.k.a. VxFS)
• Based on version from Veritas Software,
  Inc.
• Journaling
• Quick recovery after failure
• Extent based allocation
• Mount options balance
  performance/integrity

                                            18
                           VXFS Layout
                  8Kb   Super




                                 OLT




                                                            OLT
                                          Intent Log
                        Block

                           Extent
                            Map
Allocation Unit




                   AU
                                       Data/Inode Extents
                  Header


                                Data/Inode Extents

                                                             19
           File System Integrity
• Use proper shutdown procedures!
• What fsck(1M) does
  – hfs
  – vxfs
• bcheckrc



                                    20
       Mounting File Systems
• Methodology for adding a new file system
• MountPoint management
• Mounting for security
  – nosuid (!)
  – ro     (?)
• What about the device files?


                                             21
      How JFS Allocation Works


•   Files allocated into extents.
•   Extents are contiguous blocks.
•   Extents not related to LVM extents.
•   File expansion by growing extent,
•   If not, allocate new extent

                                          22
                   JFS Extents
Extent Attributes
• Adjacent disk blocks treated as a unit
• Represented by starting block and count
• Objective: Instead of Many Small I/Os, Perform Fewer Large I/Os

File Growth
• Objective is to keep file contiguous on disk
• When file grows, JFS attempts to increase size of last extent
• Otherwise, double size of current extent and relocate data
• Otherwise, allocate a new extent

Note: JFS Extents are unrelated to LVM Extents


                                                                    23
         Extent Performance
Extent Read Ahead
• Fetch more current extent than immediately
  needed
• Does NOT involve posting extra I/O
  operations

Extent Write Behinds
• Writes go to buffer cache to be flushed later
• When flushed, look for other I/O request to
  merge

                                                  24
       File System
 Consistency Check (fsck)

       HFS                     JFS

• Full Integrity      • Back-out unfinished
  Check                 transactions
• Visits all blocks   • Must explicitly
                        request full check



                                              25
     Journaled File System
               Base Features
JFS Features Beyond HFS

  •Faster file system recovery
  •Panic avoidance in JFS code
  •Improved integrity and reliability
  •Better performance due to using extents
  •HP’s strategic file system direction



                                             26
   Creating JFS Manually
•lvcreate -L 100 -n lvol2 /dev/vg04
•mkdir /test
•newfs -F vxfs /dev/vg04/rlvol2
•mount /dev/vg04/lvol2 /test

Add to /etc/fstab file:
•/dev/vg04/lvol2 /test vxfs defaults 0 2



                                           27
   Base JFS Mount Options
• Logging
  – Full Logging
  – Delayed Logging
  – Temporary logging
• Cache
  – closesync
• Others
  – Block Clear
  – No Data In Log

                            28
            Resizing Base JFS
              File Systems
• Extending
  – lvextend(1m)
  – unmount file system
  – extendfs(1m)
• Reducing
  –   backup
  –   lvreduce(1m)
  –   newfs
  –   restore

                                29
          Online JFS Features
     On Mounted File Systems, you can:
• Defragment (reorganize)
  – Remove unused spaces from directories
  – Make small files contiguous
  – Consolidate free blocks
• Resize file system while mounted
• Take a snapshot
• Modify extent attributes

                                            30
     Reporting Fragmentation
• fsadm -D   directory
• fsadm -E   extents




                               31
         Defragmentation
•   -d    directory
•   -e    extent
•   -v    verbose
•   -p    number of passes
•   -s    summarize each pass
•   -t    time limit
•   -a    how old is old
•   -l    how big is big


                                32
    Defragmenation Guidelines
• As often as necessary
• Defragment directories first
  – or both at the same time




                                 33
   Extending A File System
Extend the logical volume
  •lvextend -L 440 /dev/vg00/lvol8

Extend the JFS filesystem
  •fsadm -F vxfs -b 450560 /var

     The sector count = newLVsize * 1024




                                           34
      Reducing A File System
Backup the filesystem
   •tar cvf /dev/rmt/0m /test
Perform/view directory & extent reorganization
   •fsadm -F vxfs -d -D -e -E /test
Resize the JFS filesystem
   fsadm -F vxfs -b <newsize> /test
Reduce the size of the logical volume
   •lvreduce -L 1000 /dev/vg04/lvol2

   CAUTION: fsadm(1m) may fail to reduce!
                                                 35
        The HP-UX Journal File System

The HP-UX Journal File System (JFS) is an extent-based
journaling file system that offers:


•Fast file system recovery   •Online disk defragmentation
•Online administration       •Online reorganization
•Online backup               •Enhanced application interface
•Online resizing             •Enhanced mount options




                                                               36
        Network File Systems
• Client
  – biod
• Server
  – /etc/exports
  – nfsd
• Performance
  – nfsstat
  – number of daemons


                               37
                NFS Misc.
• Mount options
  – hard / soft
  – ro
  – never allow remote root access!
• nfs vs. ftp/rcp
• automount(1M)


                                      38
Veritas Volume Manager
        (VxVM)
– benefits of HP VERITAS Manager 3.1
– major features HP VERITAS Volume
  Manager 3.1 (VxVM)
– Volume Manager Objects
– disks and disk groups




                                       39
    Volume Manager History
– Pre-10.0: Disk sections or partitions on 800’s
– Whole disk with data (+ optional swap) on 700’s
– HP-UX 9.0 = LVM on Series 800 only
– HP-UX 8.07 = Software Disk Striping (SDS) for
  the Series 700 for 2 Gbyte disk or smaller
– HP-UX 10.0+, LVM added to 700
– HP-UX 11.11+, VxVM added to 800 only




                                               40
         Present and Future
• Present:
   – HP-UX 11i, first release of Veritas VxVM 3.1.
      • HP Workstations are not supported.
      • VxVM 3.1 cannot control the root/boot disk.
   – HP-UX 11.20 (IA-64) will support only VxVM .
      • VxVM will then be able to control the root/boot disk.
• Future:
   – Next major release - can choose either LVM or
     VxVM to be the root/boot disk.



                                                                41
HP VERITAS Volume Manager 3.1

– HP VERITAS Volume Manager 3.1 (VxVM)
  provides online disk management for HP-UX.
– Provides features not available with LVM.
  •   Java-based admin GUI and command line interface
  •   RAID-5
  •   Support for up to 32 mirrors
  •   Striped mirrors
  •   Dynamic Multi-pathing for I/O load balancing


                                                        42
 HP VERITAS Volume Manager
            3.1

• Consists of two products:
  – Base HP VERITAS Volume Manager
    (B7961AA)
     • basic volume manager features
     • included with HP-UX 11i Application Release
  – HP VERITAS Volume Manager (B9116A)
     • full set of enhanced volume manager capabilities
       including mirroring
     • requires purchase of an additional license

                                                          43
   Base HP VERITAS Volume
       Manager Overview
• Base product features:
  –   Java-based admin GUI
  –   Striping (RAID 0)
  –   Concatenation
  –   Path failover support (active/passive)
  –   Online resizing of volumes
  –   Task monitor


                                               44
              VxVM Overview
•VxVM includes all of the Base product features plus:
 –   Load-balancing -- DynamicMultiPathing (active/active)
 –   Hot-Relocation/unrelocation
 –   Mirroring (RAID-1)
 –   Supports up to 32 mirrors
 –   Mirrored Stripes (RAID 1+0)
 –   Striped Mirrors (RAID 0+1)
 –   RAID-5
 –   Online data migration
 –   Online relayout

                                                         45
     Coexistence with LVM
– VxVM coexists with LVM.
– VxVM cannot be used to control root/boot
  disk (use LVM)
– Both LVM and VxVM utilities are aware of
  each other, and will not overwrite disks that
  are being managed by the other
– Although VxVM is targeted toward new
  installations, a conversion utility:
  vxvmconvert is provided for converting LVM
  volume groups to VxVM disk groups.
                                              46
         Limitations of VxVM
• There are limitations with the first release of
  VxVM on HP-UX 11i:
   – Cannot use VxVM to control the root/boot disk. LVM
     must be the chosen volume manager for root/boot disk.
   – Disk monitor integrated with EMS framework is not
     available for disk being managed by VxVM.
   – VxVM does not support HP Process Resource Manager
     (PRM).



                                                        47
   Supported Migration Scenarios
• VxVM 3.1 is the first HP Release of the Veritas
  Volume Manager on HP-UX.
  – No migration path from Veritas Volume Manager
    3.0 on HP-UX 11.00 has been tested or is supported.
     • Product was released by Veritas, and not HP
  – VxVM 3.0 on HP-UX 11.00 users that want to
    migrate to 11i VxVM 3.1: Backup their data.
     • Upgrade to HP-UX 11i
     • Install HP VERITAS Volume Manager 3.1.


                                                     48
            HP or Veritas VxVM
– VxVM 3.0 – Contact Veritas for support
– HP/VeritasVxVM 3.1 on 11i+ supported by HP Response
  Center.
– # swlist -l product | grep vxvm
   HP Supported:
      HPvxvm 3.1 HP VERITAS Volume Manager
   Purchased from VERITAS:
      VRTSvxvm     3.X VERITAS Volume Manager
– To verify that all files belong to HPvxvm are installed:
   # swverify -v HPvxvm




                                                             49
             What is VxVM?
• VxVM operates as a subsystem between
  HP-UX and data management systems.
  – manage physical disks as logical volumes
    called volumes.
  – Volumes can span more than one physical disk.
  – provides enhanced recovery, data availability,
    performance and storage configuration options.


                                                     50
                  VxVM Objects
•VxVM uses two objects to do storage management.
 – Physical Objects
    • Physical disks
    • Partitions
 – Virtual objects
    •   VM Disks
    •   Subdisks
    •   Plexes
    •   Volumes
    •   Disk Groups


                                               51
  Conceptual Comparison
    VxVM Term             LVM Term
•VxVM Disk               •Physical Volume
•Subdisk                 •Physical Extent
•Volume                  •Logical Volume
•Disk Group              •Volume Group
•Private Region          •PVRA/BDRA/VGRA
•Free Space              •Unused Physical Extent
•Plexes                  •Mirrors
•Dirty Region Logging    •Mirror Write Cache

•Dynamic Multi-Pathing   •PV links
                                                   52
  VxVM Objects Overview
                                 Disk Group


                                    Volume
                       plex01                 plex02
                                       0                 0
                                              dg04-01
                       dg01-03                           40
                                              dg03-02
                                                         70
                                              dg02-03
                                      130               130



       VM Disk            VM Disk             VM Disk         VM Disk
                                               dg03            dg04
       dg01                  dg02

                                                        40m    dg04-01
                 60m        dg02-03     30m   dg03-02
130m   dg01-03

                                                                         53
                     VM Disk
• When a physical disk is placed under VxVM, a
  Volume Manager disk (VM Disk) is assigned to
  the physical disk.
  – A VM Disk has two regions.
     • Private Region
         – Area where VM internal configuration information is stored
     • Public Region
         – Area where storage space is allocated from
  – Each VM Disk has a unique Disk Media Name.
     • Default name that is assigned by VxVM is disk##.
     • The disk will now be referred to by its Disk Media Name
       instead of its physical address.


                                                                        54
        Example of a VM Disk
Disk under VxVM control

  VM Disk: disk01         Physical Disk

       disk01

    Private Region
                            c0t4d0
    Public Region




                                          55
                  Subdisks
– A subdisk is a set of contiguous disk blocks.
– Each subdisk represents a specific portion of a VM disk
  which is mapped to a specific region of a physical disk.
– Allocated space from the VM Disk public region
– Default name of a subdisk is disk##-##


    VM Disk: disk01       VM Disk: disk01 with one subdisk
        disk01                    disk01



                                  disk01-03
                                                 subdisk

                                                             56
     Subdisks Example
               VM Disk: disk01
Subdisks

                   disk01
disk01-01

                  disk01-01
disk01-02
                  disk01-02      Public Region

disk01-03         disk01-03




                                        57
                     Plex
– Plex consists of one or more subdisks located
  on one or more physical disks
– Plex also can be called a mirror (although it is
  one copy of the data).
– Plexes have a variety of layouts:
   • Concatenation
   • Striping (RAID-0)
   • RAID-5

                                                     58
           Plex Example
                            VM Disk: disk01
           Plex: vol01-01
                                disk01
              disk01-01
                                disk01-01
Subdisks
              disk01-02
                                disk01-02




                                            59
   Plex Layout - Concatenation
• Concatenation
  – Maps data into a linear manner onto one or
    more subdisks in a plex.
  – Space is allocated from the first subdisk from
    beginning to end. Then space is allocated from
    the remaining subdisks in a similar fashion.
  – Concatenation using subdisks that reside on
    more than one VM disk is called spanning

                                                     60
       Plex Layout - Striping
• Striping (RAID-0)
  – Maps data so that data is interleaved among two
    or more physical disks.
  – Striped plex contains two or more subdisk
    spread out over two or more physical disks.
  – Data is allocated alternately and evenly to the
    subdisks of a striped plex.


                                                 61
       Plex Layout - RAID-5
• RAID-5
  – Same as Striping but one additional column of
    data is used for parity.
  – Provides data redundancy by using Parity.
  – Requires additional license.




                                                    62
                  Plex Example
      disk01
                                 Plex01
      disk01-01

      disk01-02                           0
30m
      disk01-03              disk01-03
      disk01-04                 30m
                                          30 m
                             disk02-02
       disk02
                                 70m
                                          100m
      disk02-01
70m
      disk02-02

      disk2-03
       disk2-04                                  63
                  Volume
– Volume is a virtual disk device, but does not have
  the physical limitations of a physical disk device.
– Volume consists of one or more plexes, each
  holding a copy of the selected data in the volume.
– Volume can consist of 32 plexes, each of which
  contains one or more subdisks.
   • Never use more than 31 plexes, VxVM uses one plex
     for online (automatic or temporary) operations.
– When a volume has two or more plexes , it is a
  mirrored volume.
                                                    64
Volume Example

   Volume vol01

   plex vol01-01


     disk01-01     subdisk




                             65
Mirrored Volume Example

         Mirrored Volume vol06


   plex vol06-01    plex vol06-02

                       disk02-01
     disk01-01
                       disk04-03

                       disk03-02


                                    66
                   Disk Group
• A disk group is a collection of VM disks that share
  a common configuration
   – A disk group configuration is a set of records with
     detailed information about related VxVM objects, their
     attributes and their connections.
   – A disk group and its components can be moved as a
     unit from one host machine to another.
• Note: The rootdg (root disk group) cannot be removed
  without disrupting volume manager service to the entire
  system.
                                                          67
       Disk Group Example
                                 Disk Group


                                    Volume
                       plex01                 plex02
                                       0                 0
                                              dg04-01
                       dg01-03                           40
                                              dg03-02    70
                                              dg02-03
                                      130               130



       VM Disk            VM Disk             VM Disk         VM Disk
                                               dg03            dg04
       dg01                  dg02

                                                        40m    dg04-01
                 60m        dg02-03     30m   dg03-02
130m   dg01-03

                                                                         68
     VxVM Installation Process
           Overview
• Prior to installation:
   – Check software & hardware requirements.
   – Check disk space required to install.
   – Prepare for installing on a system with LVM
     Volume Groups
• Install VxVM:
   – Non-interactively with swinstall or
   – Interactively with swinstall

                                                   69
    Software Requirements
• Software:
  – Requires HP-UX 11i
  – VxVM is on the HP-UX 11i Application
    Release.
     • It is not on the HP-UX 11i Core Media.




                                                70
        Hardware Requirements
• Supported Platforms:
  –   N-class
  –   V-class
  –   L-class
  –   D-class 32/64 bit
  –   R-class
  –   K-class 32/64 bit

                                71
  Hardware Requirements (cont)
• Supported Peripherals:
  – HP SureStore E Disk System FC10
  – HP SureStore E Disk System SC10
  – HP SureStore E Disk Array XP256
  – HP SureStore Disk Array FC60
  – EMC Symmetrix
  – High Availability Storage System (HASS)
    A3311A/12A
  – HP SureStore E Disk Array 12H
  – HP High Availability Fibre Channel Disk Array
    Model 30/FC
  – HP High Availability SCSI Disk Array Model 2072
          Disk Space and Memory
                 Required
Additional disk space required:
    File System     Kbytes Needed
         /                21000
         /stand            2600
         /usr             11000
         /var               800
         /opt             25000
Memory:
    Minimum: 128 MB, recommended: 256 MB
•                                          73
Preparing to install on LVM system
 • Prior to installing VxVM on an LVM system
   – Review the contents of all the disks on the
     system.
   – Select at least one disk to be placed under
     VxVM control.
   – Decide whether to put any existing LVM disks
     under VxVM control.
   – Decommission any unused disks under LVM.




                                               74
           VxVM Product
• VxVM consists of two products:
  – B7961AA         - Base HP VERITAS Volume
    Manager
     • Free of charge with the HP-UX 11i Application
       Release.
  – B9116AA - HP VERITAS Volume Manager
     • The full product requires an additional purchase to
       obtain the codeword required to unlock the software.




                                                       75
           Installing VxVM

• VxVM can be installed two ways:
  – Non-interactively with swinstall
  – Interactively with swinstall


• After installing VxVM, the system will
  reboot.

                                           76
             VxVM Initialization
•After installing VxVM, run vxinstall to initialize it.
•vxinstall does the following:
 – Runs, displays the license information and prompts for key.
 – Sets up the initial VxVM disk group, rootdg, and populates it
 – Starts the configuration, notification, and relocation daemons
   used by VxVM.
•vxinstall is run only once per system
 – Used to setup rootdg if it does not exist.
 – Exception is special troubleshooting situations.


                                                            77
First VxVM Disk Group: rootdg
• VxVM cannot be used until rootdg is set up
  and at least one disk is assigned.
  – One disk must remain under rootdg at all times
    while VxVM is running.
  – Despite its name, rootdg will not be the system
    root disk, as VxVM cannot be used to control
    the root/boot disk.
  – LVM will control the root/boot disk.

                                                 78
     Verify VxVM has initialized

• After the installation is complete, run the
  following command to verify that the key VxVM
  processes are running:
  ps -ef | grep vx
  output should include the following VxVM processes:
     •   vxiod
     •   vxnotify
     •   vxrelocd
     •   vxconfigd




                                                        79
            VxVM Utilities
• VxVM provides the following user
  interfaces that can be used to manage disks:
  – VMSA - graphical user interface
  – vxdiskadm - interactive menu-based interface
  – CLI - Command-Line Interface




                                                   80
        Setting up the Storage
         Administrator GUI
• The Storage Administrator, VMSA, is the Java
  based interface for VxVM.
  – Installed as part of the Base HP VxVM.
  – After initializing VxVM with vxinstall, you must set up
    VMSA.
  – VMSA consists of a server and a client:
     • The server (vmsa_server) must be installed and run on a HP-
       UX 11i machine with VxVM.
     • The client (vmsa) is the graphical user interface. It must be
       installed and run on an HP-UX 11i machine that supports the
       Java 1.1 Runtime Environment.

                                                                       81
              Starting VMSA
– Log in as root.
– Create and export VMSAHOME variable
  # export VMSAHOME=/opt/HPvmsa
– Update PATH variable to include
  $VMSAHOME/bin
– It may be helpful to include these variables in your
  .profile.
– To start the server run:
   # vmsa_server &
– To start the client
  #xhost + hostname
  #         vmsa &


                                                         82
      Customizing Security
– By default, only root can run VMSA.
– The system can be set up to allow other users to
  run VMSA by:
   • Adding a group name vrtsadm to /etc/group
   • Specifying users, including root, as vrtsadm
     members.
– VMSA can also be configured in read-only
  mode.
   • This mode is enabled via the properties file.
     /opt/HPvmsa/vmsa/properties
                                                     83
             VMSA commands
    – Query the run state of the server:
•      # vmsa_server -q

    – Kill the Server:
•      # vmsa_server -k

    – Show the VMSA version number:
•      # vmsa_server -v
                                           84
               VMSA GUI
  Toolbar



                               Grid
 Object tree




Command
 launcher




                          85
     Useful CLI commands

– vxassist - Create and manage volumes in a
  single step.
– vxprint - List VxVM information.
– vxdg - Create and manage disk groups.
– vxdisk - Create and manage VM Disks.
– Some CLI commands can be found in the
  /etc/vx/bin directory.
   • Add this directory to $PATH

                                              86
          Removing VxVM
• Before removing VxVM software using
  swremove, you must:
  – Do a full backup of your data.
  – Move data out of VxVM control.
  – Stop VxVM.




                                        87
                    Summary
• VxVM is an LVM-like tool
• Much more powerful and complex
• Much more versatility
  –   Striping
  –   Mirroring (up to 31, not just 3)
  –   Stripe and mirror
  –   RAID 5 data protection
  –   And more
                                         88

				
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posted:9/3/2011
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