Red Hat ENTERPRISE LINUX 4 - LVM ADMINISTRATOR Guida di Installazione

Red Hat Enterprise Linux 6Logical VolumeManager AdministrationLVM Administrator Guide

IntroductionxPublican is a DocBook publishing system.6.2. Pull-quote ConventionsTerminal output and source code listings are set off visually from the

Appendix A. The Device Mapper88The following example shows a pure failover target definition for the same multipath device. In thistarget there are fo

The dmsetup Command89deviceblock device, referenced by the device name in the filesystem or by the major and minor numbersin the format major:minoroff

Appendix A. The Device Mapper90Event numberThe current number of events received. Issuing a dmsetup wait n command allows the userto wait for the n&a

The dmsetup status Command91[root@grant-01 ~]# dmsetup ls --target mirrorlock_stress-grant--02.1722 (253, 34)lock_stress-grant--01.1720 (253

Appendix A. The Device Mapper92The following example shows the command to list the dependencies of all currently configuredmapped devices.[root@ask-07

udev Integration with the Device Mapper93and LVM). Without this support, it was a common problem for a user to try to remove a device that wasstill op

Appendix A. The Device Mapper94• DM_SUSPENDED: the suspended state of Device Mapper device• DM_UDEV_RULES_VSN: udev rules version (this is primarily f

Commands and Interfaces that Support udev95 dmsetup command ... ... dmsetup command ...--noudevrulesDisables udev rules. Nodes/symlinks will be cre

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97Appendix B. The LVM ConfigurationFilesLVM supports multiple configuration files. At system startup, the lvm.conf configuration file is loadedfrom th

Notes and WarningsxiWarningWarnings should not be ignored. Ignoring warnings will most likely cause data loss.

Appendix B. The LVM Configuration Files98# the environment variable LVM_SYSTEM_DIR before running the tools.## N.B. Take care that each setting only a

Sample lvm.conf File99 # filter =[ "a|loop|", "r|/dev/hdc|", "a|/dev/ide|", "r|.*|" ] # Use anchors if y

Appendix B. The LVM Configuration Files100 # But note that pvcreate --dataalignmentoffset will skip this detection. # 1 enables; 0 disables.

Sample lvm.conf File101# Set to 1 to guarantee that mirror logs will always be placed on # different PVs from the mirror images. This was the d

Appendix B. The LVM Configuration Files102 backup_dir = "/etc/lvm/backup" # Should we maintain an archive of old metadata configuratio

Sample lvm.conf File103 # The default metadata format that commands should use - "lvm1" or "lvm2". # The command line overri

Appendix B. The LVM Configuration Files104 # If set to 1, no operations that change on-disk metadata will be permitted. # Additionally, read-onl

Sample lvm.conf File105 reserved_stack = 256 # How much memory (in KB) to reserve for use while devices suspended reserved_memory = 8192 #

Appendix B. The LVM Configuration Files106 # snapshot should be extended: when its space usage exceeds this many # percent. The latter defines h

Sample lvm.conf File107 # are used at the individual PV level using 'pvchange # --metadataignore y/n'. # vgmetadatacopies = 0 #

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109Appendix C. LVM Object TagsAn LVM tag is a word that can be used to group LVM2 objects of the same type together. Tags canbe attached to objects su

Appendix C. LVM Object Tags110For example, the following entry in the configuration file always defines tag1, and defines tag2 if thehostname is host1

111Appendix D. LVM Volume GroupMetadataThe configuration details of a volume group are referred to as the metadata. By default, an identicalcopy of th

Appendix D. LVM Volume Group Metadata112• A version number which is incremented whenever the metadata gets updated• Any properties: Read/Write? Resize

Sample Metadata113 status = ["ALLOCATABLE"] dev_size = 35964301 # 17.1491 Gigabytes

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115Appendix E. Revision HistoryRevision 3.0-5 Thu Dec 1 2011 Steven Levine [email protected] for GA of Red Hat Enterprise Linux 6.2Revision 3.

Appendix E. Revision History116Documents support for including multiple --addtag and --deltag arguments on a single commandline.Resolves: #694604Docum

117IndexSymbols/lib/udev/rules.d directory, 93Aactivating logical volumesindividual nodes, 49activating volume groups, 30individual nodes, 30local nod

Chapter 1.1The LVM Logical Volume ManagerThis chapter provides a summary of the features of the LVM logical volume manager that are new forthe initial

Index118displaying, 43, 49, 54exclusive access, 49extending, 43growing, 43linear, 32local access, 49lvs display arguments, 54mirrored, 34reducing, 47r

119report format, LVM devices, 49resizinglogical volume, 42physical volume, 25rules.d directory, 93Sscanningblock devices, 23scanning devices, filters

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Chapter 1. The LVM Logical Volume Manager2• You can now create a mirror log for a mirrored logical device that is itself mirrored by using the --mirro

LVM Architecture Overview3Volume management creates a layer of abstraction over physical storage, allowing you to createlogical storage volumes. This

Chapter 1. The LVM Logical Volume Manager4• atomic changes to metadata• redundant copies of metadataLVM2 is backwards compatible with LVM1, with the e

The Clustered Logical Volume Manager (CLVM)5• If you are using a clustered system for failover where only a single node that accesses the storageis ac

Chapter 1. The LVM Logical Volume Manager6Figure 1.2. CLVM OverviewNoteCLVM requires changes to the lvm.conf file for cluster-wide locking. Informatio

Document Overview7• Chapter 3, LVM Administration Overview provides an overview of the basic steps you perform toconfigure LVM logical volumes, whethe

Logical Volume Manager AdministrationRed Hat Enterprise Linux 6 Logical Volume ManagerAdministrationLVM Administrator GuideEdition 1Copyright © 2011 R

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Chapter 2.9LVM ComponentsThis chapter describes the components of an LVM Logical volume.2.1. Physical VolumesThe underlying physical storage unit of a

Chapter 2. LVM Components10Figure 2.1. Physical Volume layout2.1.2. Multiple Partitions on a DiskLVM allows you to create physical volumes out of disk

LVM Logical Volumes11A logical volume is allocated into logical extents of the same size as the physical extents. The extentsize is thus the same for

Chapter 2. LVM Components12of 4MB. This volume group includes 2 physical volumes named PV1 and PV2. The physical volumesare divided into 4MB units, si

Mirrored Logical Volumes13striped logical volume. For large sequential reads and writes, this can improve the efficiency of thedata I/O.Striping enhan

Chapter 2. LVM Components14A mirror maintains identical copies of data on different devices. When data is written to one device, itis written to a sec

Snapshot Volumes15NoteLVM snapshots are not supported for LVM mirrored logical volumes.Because a snapshot copies only the data areas that change after

Chapter 2. LVM Components16As of the Red Hat Enterprise Linux 6 release, you can use the --merge option of the lvconvertcommand to merge a snapshot in

Chapter 3.17LVM Administration OverviewThis chapter provides an overview of the administrative procedures you use to configure LVM logicalvolumes. Thi

iiiIntroduction vii1.

Chapter 3. LVM Administration Overview18The following is a summary of the steps to perform to create an LVM logical volume.1. Initialize the partition

Logging19in the /etc/lvm/backup file and the metadata archives are stored in the /etc/lvm/archivefile. How long the metadata archives stored in the /e

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Chapter 4.21LVM Administration with CLICommandsThis chapter summarizes the individual administrative tasks you can perform with the LVM CommandLine In

Chapter 4. LVM Administration with CLI Commands22 Found volume group "new_vg" Creating new_vg-lvol0 Loading new_vg-lvol0 table R

Creating Physical Volumes23The following subsections describe the commands used for creating physical volumes.4.2.1.1. Setting the Partition TypeIf yo

Chapter 4. LVM Administration with CLI Commands24 /dev/ram8 [ 16.00 MB] /dev/ram9 [ 16.00 MB] /de

Preventing Allocation on a Physical Volume25You can define a filter in the lvm.conf so that this command will avoid scanning specific physicalvolumes.

Chapter 4. LVM Administration with CLI Commands26# vgcreate vg1 /dev/sdd1 /dev/sde1When physical volumes are used to create a volume group, its disk s

Adding Physical Volumes to a Volume Group27You create volume groups in a cluster environment with the vgcreate command, just as you createthem on a si

Logical Volume Manager Administrationiv4.3.9. Removing Volume Groups ...

Chapter 4. LVM Administration with CLI Commands28For information on using the vgs command to customize your output, see Section 4.8, “CustomizedReport

Removing Physical Volumes from a Volume Group29# vgscan Reading all physical volumes. This may take a while... Found volume group "new_vg"

Chapter 4. LVM Administration with CLI Commands304.3.8. Activating and Deactivating Volume GroupsWhen you create a volume group it is, by default, act

Backing Up Volume Group Metadata31extent sizes of the volume are equal and the physical and logical volume summaries of both volumegroups fit into the

Chapter 4. LVM Administration with CLI Commands323. Use the vgexport command to export the volume group. This prevents it from being accessed bythe sy

Creating Linear Logical Volumes33The following command creates a 1500 MB linear logical volume named testlv in the volume grouptestvg, creating the bl

Chapter 4. LVM Administration with CLI Commands34You can specify which extents of a physical volume are to be used for a logical volume. The following

Creating Mirrored Volumes35Mirrored LVM Logical Volumes in a ClusterCreating a mirrored LVM logical volume in a cluster requires the same commands and

Chapter 4. LVM Administration with CLI Commands36LVM maintains a small log which it uses to keep track of which regions are in sync with the mirror or

Creating Mirrored Volumes37When a mirror is created, the mirror regions are synchronized. For large mirror components, the syncprocess may take a long

v6.2. Displaying Information on Failed Devices ... 696.3. Recovering from LVM Mirror

Chapter 4. LVM Administration with CLI Commands38By default, the mirror_image_fault_policy parameter is set to remove. With this policy, if amirror im

Creating Snapshot Volumes39specified by the mirror_log_fault_policy and mirror_device_fault_policy parametersin the lvm.conf file.4.4.3.4. Changing Mi

Chapter 4. LVM Administration with CLI Commands40NoteAs of the Red Hat Enterprise Linux 6.1 release, LVM snapshots are supported for mirrored logicalv

Merging Snapshot Volumes41WarningBecause the snapshot increases in size as the origin volume changes, it is important to monitorthe percentage of the

Chapter 4. LVM Administration with CLI Commands424.4.7. Resizing Logical VolumesTo reduce the size of a logical volume, use the lvreduce command. If t

Displaying Logical Volumes43[root@tng3-1 lvm]# lvremove /dev/testvg/testlvDo you really want to remove active logical volume "testlv"? [y/n]

Chapter 4. LVM Administration with CLI Commands44# lvextend -L+1G /dev/myvg/homevollvextend -- extending logical volume "/dev/myvg/homevol"

Growing Logical Volumes45The following command adds another physical volume to the volume group, which then has 135G ofadditional space.# vgextend vg

Chapter 4. LVM Administration with CLI Commands46For example, if you have logical volumes that are mirrored between two sites within a single volumegr

Shrinking Logical Volumes47[root@taft-03 ~]# lvs -a -o +devices LV VG Attr LSize Log Copy% Devices mirror

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Chapter 4. LVM Administration with CLI Commands48filter = [ "a/.*/" ]The following filter removes the cdrom device in order to avoid delays

Activating Logical Volumes on Individual Nodes in a Cluster49# pvmove -i5 /dev/sdd14.7. Activating Logical Volumes on Individual Nodes in aClusterIf y

Chapter 4. LVM Administration with CLI Commands50 /dev/sdb1 17.14G /dev/sdc1 17.14G /dev/sdd1 17.14G• You can append a field to the output with

Object Selection51 /dev/sdd1 =new_vg=lvm2=a- =17.14G=17.14GYou can use the -P argument of the lvs or vgs command to display information about a fail

Chapter 4. LVM Administration with CLI Commands52Argument Header Descriptionpv_name PV The physical volume namepv_pe_alloc_count Alloc Number of used

Object Selection53 /dev/sdb1 vg lvm2 a- 17.14G 17.14G 0 4389 /dev/sdc1 vg lvm2 a- 17.14G 17.14G 0 4389 /dev/sdd1 v

Chapter 4. LVM Administration with CLI Commands54Argument Header Descriptionvg_free_count Free Number of free physical extents in the volume groupvg_n

Object Selection55Argument Header DescriptionBit 3: Allocation policy: (c)ontiguous, (n)ormal,(a)nywhere, (i)nherited. This is capitalized if the volu

Chapter 4. LVM Administration with CLI Commands56# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert lvol0 new_vg owi-a

Sorting LVM Reports574.8.3. Sorting LVM ReportsNormally the entire output of the lvs, vgs, or pvs command has to be generated and stored internallybef

viiIntroduction1. About This GuideThis book describes the Logical Volume Manager (LVM), including information on running LVM in aclustered environment

Chapter 4. LVM Administration with CLI Commands58# pvs --units m PV VG Fmt Attr PSize PFree /dev/sda1 lvm2 -- 17555.40M 1

Chapter 5.59LVM Configuration ExamplesThis chapter provides some basic LVM configuration examples.5.1. Creating an LVM Logical Volume on Three DisksTh

Chapter 5. LVM Configuration Examples60[root@tng3-1 ~]# mkfs.gfs2 -plock_nolock -j 1 /dev/new_vol_group/new_logical_volumeThis will destroy any data o

Creating the Logical Volume61You can use the vgs command to display the attributes of the new volume group.[root@tng3-1 ~]# vgs VG #PV

Chapter 5. LVM Configuration Examples62In the initial set up, the logical volume mylv is carved from the volume group myvol, which in turnconsists of

Creating the New Logical Volume63 Volume group "yourvg" successfully split from "myvg"You can use the vgs command to see the attr

Chapter 5. LVM Configuration Examples64This example shows how you can remove a disk from an existing logical volume, either to replace thedisk or to u

Moving Extents to a New Disk65[root@tng3-1]# pvs -o+pv_used PV VG Fmt Attr PSize PFree Used /dev/sda1 myvg lvm2 a- 17.15G 7.15G 10.

Chapter 5. LVM Configuration Examples665.5. Creating a Mirrored LVM Logical Volume in a ClusterCreating a mirrored LVM logical volume in a cluster req

Creating a Mirrored LVM Logical Volume in a Cluster675. Create the mirror. The first step is creating the physical volumes. The following commands cre

Introductionviii• Release Notes — Provides information about the current release of Red Hat products.High Availability Add-On documentation and other

Chapter 5. LVM Configuration Examples68May 10 14:55:00 doc-07 lvm[19402]: vg001-mirrorlv is now in-sync8. You can use the lvs with the -o +devices opt

Chapter 6.69LVM TroubleshootingThis chapter provide instructions for troubleshooting a variety of LVM issues.6.1. Troubleshooting DiagnosticsIf a comm

Chapter 6. LVM Troubleshooting70[root@link-07 tmp]# lvs -a -o +devices Volume group "vg" not foundUsing the -P argument shows the logical v

Recovering from LVM Mirror Failure71 Physical volume "/dev/sdc1" successfully created Physical volume "/dev/sdc2" successfully c

Chapter 6. LVM Troubleshooting72 groupfs vg -wi-a- 752.00M /dev/sdb1(0)At this point you should still be able to use

Recovering Physical Volume Metadata73 Logical volume mirror converted.You can use the lvs command to verify that the mirror is restored.[root@link-08

Chapter 6. LVM Troubleshooting74indicated above, FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk. This command restores thephysical volume label with the metad

Removing Lost Physical Volumes from a Volume Group756.6. Removing Lost Physical Volumes from a Volume GroupIf you lose a physical volume, you can acti

Chapter 6. LVM Troubleshooting76Alternately, you can extend the logical volume to use a percentage of the remaining free spacein the volume group by u

Chapter 7.77LVM Administration with the LVM GUIIn addition to the Command Line Interface (CLI), LVM provides a Graphical User Interface (GUI)which you

Typographic ConventionsixPress Ctrl+Alt+F2 to switch to the first virtual terminal. Press Ctrl+Alt+F1 toreturn to your X-Windows session.The first par

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79Appendix A. The Device MapperThe Device Mapper is a kernel driver that provides a framework for volume management. It providesa generic way of creat

Appendix A. The Device Mapper80• mirror• snapshot and snapshot-origin• error• zero• multipath• cryptA.1.1. The linear Mapping TargetA linear mapping t

The striped Mapping Target81startstarting block in virtual devicelengthlength of this segment#stripesnumber of stripes for the virtual devicechunk_siz

Appendix A. The Device Mapper820 65536 striped 2 512 /dev/hda 0 /dev/hdb 0A.1.3. The mirror Mapping TargetThe mirror mapping target supports the mappi

The snapshot and snapshot-origin Mapping Targets83logargsthe log arguments for the mirror; the number of log arguments provided is specified by the #l

Appendix A. The Device Mapper841. A device with a linear mapping containing the original mapping table of the source volume.2. A device with a linear

The error Mapping Target85startstarting block in virtual devicelengthlength of this segmentoriginbase volume of snapshotCOW-deviceDevice on which chan

Appendix A. The Device Mapper86The zero mapping target takes no additional parameters besides the start and lengthparameters.The following example sho

The multipath Mapping Target87pathgroupThe next path group to try.pathgroupsargsEach path group consists of the following arguments:pathselector #sele