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3. Recovering from LVM Mirror Failure

This section provides an example of recovering from a situation where one leg of an LVM

mirrored volume fails because the underlying device for a physical volume goes down. When a

mirror leg fails, LVM converts the mirrored volume into a linear volume, which continues to

operate as before but without the mirrored redundancy. At that point, you can add a new disk

device to the system to use as a replacement physical device and rebuild the mirror.

The following command creates the physical volumes which will be used for the mirror.

[root@link-08 ~]# pvcreate /dev/sd[abcdefgh][12]

Physical volume "/dev/sda1" successfully created

Physical volume "/dev/sda2" successfully created

Physical volume "/dev/sdb1" successfully created

Physical volume "/dev/sdb2" successfully created

Physical volume "/dev/sdc1" successfully created

Physical volume "/dev/sdc2" successfully created

Physical volume "/dev/sdd1" successfully created

Physical volume "/dev/sdd2" successfully created

Physical volume "/dev/sde1" successfully created

Physical volume "/dev/sde2" successfully created

Physical volume "/dev/sdf1" successfully created

Physical volume "/dev/sdf2" successfully created

Physical volume "/dev/sdg1" successfully created

Physical volume "/dev/sdg2" successfully created

Physical volume "/dev/sdh1" successfully created

Physical volume "/dev/sdh2" successfully created

The following commands creates the volume group

and the mirrored volume

groupfs

[root@link-08 ~]# vgcreate vg /dev/sd[abcdefgh][12]

Volume group "vg" successfully created

[root@link-08 ~]# lvcreate -L 750M -n groupfs -m 1 vg /dev/sda1 /dev/sdb1

/dev/sdc1

Rounding up size to full physical extent 752.00 MB

Logical volume "groupfs" created

You can use the

lvs

command to verify the layout of the mirrored volume and the underlying

devices for the mirror leg and the mirror log. Note that in the first example the mirror is not yet

completely synced; you should wait until the

Copy%

field displays 100.00 before continuing.

[root@link-08 ~]# lvs -a -o +devices

Attr

LSize

Origin Snap%

Move Log

Copy% Devices

groupfs

mwi-a- 752.00M

groupfs_mlog

21.28 groupfs_mimage_0(0),groupfs_mimage_1(0)

[groupfs_mimage_0] vg

iwi-ao 752.00M

/dev/sda1(0)

[groupfs_mimage_1] vg

iwi-ao 752.00M

Recovering from LVM Mirror Failure

Содержание GLOBAL FILE SYSTEM 5.0

Страница 1: ...LVM Administrator s Guide Configuration and Administration 5 0 ISBN N A Publication date...

Страница 2: ...his book describes the LVM logical volume manager including information on running LVM in a clustered environment The content of this document is specific to the LVM2 release LVM Administrator s Guide...

Страница 3: ...cument is prohibited without the explicit permission of the copyright holder Distribution of the work or derivative of the work in any standard paper book form for commercial purposes is prohibited un...

Страница 4: ...LVM Administrator s Guide...

Страница 5: ...ume Creation Overview 17 3 Growing a File System on a Logical Volume 18 4 Logical Volume Backup 18 5 Logging 19 4 LVM Administration with CLI Commands 21 1 Using CLI Commands 21 2 Physical Volume Admi...

Страница 6: ...ting for LVM 47 9 1 Format Control 47 9 2 Object Selection 49 9 3 Sorting LVM Reports 56 9 4 Specifying Units 57 5 LVM Configuration Examples 59 1 Creating an LVM Logical Volume on Three Disks 59 1 1...

Страница 7: ...Group 76 7 Insufficient Free Extents for a Logical Volume 76 7 LVM Administration with the LVM GUI 79 A The Device Mapper 81 B The LVM Configuration Files 83 1 The LVM Configuration Files 83 2 Sample...

Страница 8: ...viii...

Страница 9: ...Hat Enterprise Linux refer to the following resources Red Hat Enterprise Linux Installation Guide Provides information regarding installation of Red Hat Enterprise Linux 5 Red Hat Enterprise Linux Dep...

Страница 10: ...s file names and paths and prompts When shown as below it indicates computer output Desktop about html logs paulwesterberg png Mail backupfiles mail reports bold Courier font Bold Courier font represe...

Страница 11: ...tion indicates an act that would violate your support agreement such as recompiling the kernel Warning A warning indicates potential data loss as may happen when tuning hardware for maximum performanc...

Страница 12: ...h version of the guide you have If you have a suggestion for improving the documentation try to be as specific as possible If you have found an error please include the section number and some of the...

Страница 13: ...hen using logical volumes file systems can extend across multiple disks since you can aggregate disks and partitions into a single logical volume Resizeable storage pools You can extend logical volume...

Страница 14: ...LVM1 with the exception of snapshot and cluster support You can convert a volume group from LVM1 format to LVM2 format with the vgconvert command For information on converting LVM metadata format see...

Страница 15: ...ions to LVM These extensions allow a cluster of computers to manage shared storage for example on a SAN using LVM The clmvd daemon is the key clustering extension to LVM The clvmd daemon runs in each...

Страница 16: ...ric infrastructure Note Shared storage for use in Red Hat Cluster Suite requires that you be running the cluster logical volume manager daemon clvmd or the High Availability Logical Volume Management...

Страница 17: ...configure LVM logical volumes whether you are using the LVM Command Line Interface CLI commands or the LVM Graphical User Interface GUI Chapter 4 LVM Administration with CLI Commands summarizes the in...

Страница 18: ...6...

Страница 19: ...the LVM metadata will be stored on the device The LVM metadata contains the configuration details of the LVM volume groups on your system By default an identical copy of the metadata is maintained in...

Страница 20: ...is becomes particularly true if a disk fails In addition multiple physical volumes on a single disk may cause a kernel warning about unknown partition types at boot up Striping performance LVM can not...

Страница 21: ...sical extents A logical volume is allocated into logical extents of the same size as the physical extents The extent size is thus the same for all logical volumes in the volume group The volume group...

Страница 22: ...ze of 4MB This volume group includes 2 physical volumes named PV1 and PV2 The physical volumes are divided into 4MB units since that is the extent size In this example PV1 is 100 extents in size 400MB...

Страница 23: ...from the pool of physical extents Figure 2 4 Multiple Logical Volumes shows the same volume group as in Figure 2 3 Linear Volume with Unequal Physical Volumes but in this case two logical volumes have...

Страница 24: ...a to a predetermined number of physical volumes in round round fashion With striping I O can be done in parallel In some situations this can result in near linear performance gain for each additional...

Страница 25: ...9 Extending a Striped Volume 3 3 Mirrored Logical Volumes A mirror maintains identical copies of data on different devices When data is written to one device it is written to a second device as well...

Страница 26: ...te Mirrored logical volumes are not currently supported in a cluster For information on creating and modifying mirrors see Section 4 1 3 Creating Mirrored Volumes 3 4 Snapshot Volumes The LVM snapshot...

Страница 27: ...ee up space that is needed by other logical volumes When you create a snapshot file system full read and write access to the origin stays possible If a chunk on a snapshot is changed that chunk is mar...

Страница 28: ...16...

Страница 29: ...infrastructure must be running and the cluster must be quorate Note Shared storage for use in Red Hat Cluster Suite requires that you be running the cluster logical volume manager daemon clvmd or the...

Страница 30: ...growing to include the new physical volume 3 Extend the logical volume to include the new physical volume 4 Grow the file system If you have sufficient unallocated space in the volume group you can us...

Страница 31: ...ging All message output passes through a logging module with independent choices of logging levels for standard output error syslog log file external log function The logging levels are set in the etc...

Страница 32: ...20...

Страница 33: ...units argument in a command lower case indicates that units are in multiples of 1024 while upper case indicates that units are in multiples of 1000 Where commands take volume group or logical volume n...

Страница 34: ...te vvvv L 50MB new_vg lvmcmdline c 913 Processing lvcreate vvvv L 50MB new_vg lvmcmdline c 916 O_DIRECT will be used config config c 864 Setting global locking_type to 1 locking locking c 138 File bas...

Страница 35: ...t have no partition table For DOS disk partitions the partition id should be set to 0x8e using the fdisk or cfdisk command or an equivalent For whole disk devices only the partition table must be eras...

Страница 36: ...hysical volume dev sdd 17 15 GB dev sdd1 17 14 GB LVM physical volume 7 disks 17 partitions 0 LVM physical volume whole disks 4 LVM physical volumes 2 2 Displaying Physical Volumes There are three com...

Страница 37: ...information on using filters to control which devices are scanned see Section 6 Controlling LVM Device Scans with Filters 2 3 Preventing Allocation on a Physical Volume You can prevent allocation of p...

Страница 38: ...volume to it The following command creates a volume group named vg1 that contains physical volumes dev sdd1 and dev sde1 vgcreate vg1 dev sdd1 dev sde1 When physical volumes are used to create a volum...

Страница 39: ...out dev vg lv For example if you create two volume groups myvg1 and myvg2 each with three logical volumes named lvo1 lvo2 and lvo3 this create six device special files dev myvg1 lv01 dev myvg1 lv02 de...

Страница 40: ...13164 Alloc PE Size 13 52 00 MB Free PE Size 13151 51 37 GB VG UUID jxQJ0a ZKk0 OpMO 0118 nlwO wwqd fD5D32 3 4 Scanning Disks for Volume Groups to Build the Cache File The vgscan command scans all sup...

Страница 41: ...ing a physical volume from a volume group you can make sure that the physical volume is not used by any logical volumes by using the pvdisplay command pvdisplay dev hda1 Physical volume PV Name dev hd...

Страница 42: ...To deactivate or activate a volume group use the a available argument of the vgchange command The following example deactivates the volume group my_volume_group vgchange a n my_volume_group If cluste...

Страница 43: ...nation volume groups limits The following command merges the inactive volume group my_vg into the active or inactive volume group databases giving verbose runtime information vgmerge v databases my_vg...

Страница 44: ...prevents any further activity on the volume group 3 Use the vgexport command to export the volume group This prevents it from being accessed by the system from which you are removing it After you expo...

Страница 45: ...sed where is the internal number of the logical volume The following sections provide examples of logical volume creation for the three types of logical volumes you can create with LVM 4 1 1 Creating...

Страница 46: ...command to find the Total PE size and to use those results as input to the the lvcreate command The following commands create a logical volume called mylv that fills the volume group named testvg vgd...

Страница 47: ...the lvcreate command This determines over how many physical volumes the logical volume will be striped The number of stripes cannot be greater than the number of physical volumes in the volume group u...

Страница 48: ...t persistent across reboots You can specify instead that this log be kept in memory with the corelog argument this eliminates the need for an extra log device but it requires that the entire mirror be...

Страница 49: ...0 4 1 4 Changing Mirrored Volume Configuration You can convert a logical volume from a mirrored volume to a linear volume or from a linear volume to a mirrored volume with the lvconvert command You c...

Страница 50: ...contains a file system be sure to reduce the file system first or use the LVM GUI so that the logical volume is always at least as large as the file system expects it to be The following command reduc...

Страница 51: ...stvg testlv from the volume group testvg Note that in this case the logical volume has not been deactivated root tng3 1 lvm lvremove dev testvg testlv Do you really want to remove active logical volum...

Страница 52: ...ogical volumne dev myvg homevol to 12 gigabytes lvextend L12G dev myvg homevol lvextend extending logical volume dev myvg homevol to 12 GB lvextend doing automatic backup of volume group myvg lvextend...

Страница 53: ...way stripe that that uses up an entire volume group adding a single physical volume to the volume group will not enable you to extend the stripe Instead you must add at least two physical volumes to...

Страница 54: ...sdd1 Volume group vg successfully extended vgs VG PV LV SN Attr VSize VFree vg 4 1 0 wz n 542 62G 271 31G lvextend vg stripe1 L 542G Using stripesize of last segment 64 00 KB Extending logical volume...

Страница 55: ...snapshot volume is writeable LVM snapshots are not cluster aware so they require exclusive access to a volume For information on activating logical volumes on individual nodes in a cluster see Sectio...

Страница 56: ...pshot volume dev new_vg newvgsnap has been created lvs LV VG Attr LSize Origin Snap Move Log Copy lvol0 new_vg owi a 52 00M newvgsnap1 new_vg swi a 8 00M lvol0 0 20 Note Because the snapshot increases...

Страница 57: ...following filter adds all discovered devices which is the default behavior as there is no filter configured in the configuration file filter a The following filter removes the cdrom device in order t...

Страница 58: ...mand in the background to avoid display of progress updates in the foreground The following command moves all extents allocated to to the physical volume dev sdc1 over to dev sdf1 in the background pv...

Страница 59: ...ontrol the format of the generated report A list of the fields you can select for each LVM object A summary of command arguments you can use to sort the generated report Instructions for specifying th...

Страница 60: ...PV VG Fmt Attr PSize PFree DevSize PV UUID dev sdb1 new_vg lvm2 a 17 14G 17 14G 17 14G onFF2w 1fLC ughJ D9eB M7iv 6XqA dqGeXY dev sdc1 new_vg lvm2 a 17 14G 17 09G 17 14G Joqlch yWSj kuEn IdwM 01S9 XO...

Страница 61: ...Volume group fields can be mixed with either physical volume and physical volume segment fields or with logical volume and logical volume segment fields but physical volume and logical volume fields c...

Страница 62: ...physical extents pv_pe_count PE Number of physical extents pvseg_size SSize The segment size of the physical volume pvseg_start Start The starting physical extent of the physical volume segment pv_si...

Страница 63: ...Size PFree Start SSize dev hda2 VolGroup00 lvm2 a 37 16G 32 00M 0 1172 dev hda2 VolGroup00 lvm2 a 37 16G 32 00M 1172 16 dev hda2 VolGroup00 lvm2 a 37 16G 32 00M 1188 1 dev sda1 vg lvm2 a 17 14G 16 75G...

Страница 64: ...he volume group contains vg_attr Attr Status of the volume group w riteable r eadonly resi z eable e x ported p artial and c lustered vg_extent_count Ext The number of physical extents in the volume g...

Страница 65: ...ical volume also used when physical extents are being moved with the pv_move command devices Devices The underlying devices that make up the logical volume the physical volumes logical volumes and sta...

Страница 66: ...e pvmove command origin Origin The origin device of a snapshot volume regionsize region_size Region The unit size of a mirrored logical volume seg_count Seg The number of segments in the logical volum...

Страница 67: ...s by default lv_name vg_name lv_attr stripes segtype seg_size The default display is sorted by vg_name lv_name within the volume group and seg_start within the logical volume If the logical volumes we...

Страница 68: ...elds within the output itself The following example shows the output of the pvs command that displays the physical volume name size and free space pvs o pv_name pv_size pv_free PV PSize PFree dev sdb1...

Страница 69: ...555 40M 17555 40M dev sdb1 new_vg lvm2 a 17552 00M 17552 00M dev sdc1 new_vg lvm2 a 17552 00M 17500 00M dev sdd1 new_vg lvm2 a 17552 00M 17552 00M By default units are displayed in powers of 2 multipl...

Страница 70: ...new_vg lvm2 a 35946496S 35840000S dev sdd1 new_vg lvm2 a 35946496S 35946496S The following example displays the output of the pvs command in units of 4 megabytes pvs units 4m PV VG Fmt Attr PSize PFre...

Страница 71: ...dev sda1 successfully created Physical volume dev sdb1 successfully created Physical volume dev sdc1 successfully created 1 2 Creating the Volume Group The following command creates the volume group n...

Страница 72: ...roups 8 Locking Protocol lock_nolock Lock Table Syncing All Done The following commands mount the logical volume and report the file system disk space usage root tng3 1 mount dev new_vol_group new_log...

Страница 73: ...e striped_vol_group 3 0 0 wz n 51 45G 51 45G 2 3 Creating the Logical Volume The following command creates the striped logical volume striped_logical_volume from the volume group striped_vol_group Thi...

Страница 74: ...xample an existing volume group consists of three physical volumes If there is enough unused space on the physical volumes a new volume group can be created without adding new disks In the initial set...

Страница 75: ...ume group yourvg use the vgsplit command to split the volume group myvg Before you can split the volume group the logical volume must be inactive If the file system is mounted you must unmount the fil...

Страница 76: ...Filesystem Size 1277816 Journals 1 Resource Groups 20 Locking Protocol lock_nolock Lock Table Syncing All Done root tng3 1 mount dev yourvg yourlv mnt 3 6 Activating and Mounting the Original Logical...

Страница 77: ...lumes in the volume group you can execute the pvmove command on the device you want to remove with no other options and the extents will be distributed to the other devices root tng3 1 pvmove dev sdb1...

Страница 78: ...w Physical Volume Create a new physical volume from dev sdd1 root tng3 1 pvcreate dev sdd1 Physical volume dev sdd1 successfully created 4 2 2 Adding the New Physical Volume to the Volume Group Add de...

Страница 79: ...g lvm2 a 17 15G 15 15G 2 00G dev sdd1 myvg lvm2 a 17 15G 15 15G 2 00G 4 2 4 Removing the Old Physical Volume from the Volume Group After you have moved the data off dev sdb1 you can remove it from the...

Страница 80: ...68...

Страница 81: ...command for additional system information Examine the last backup of the metadata in the etc lvm backup file and archived versions in the etc lvm archive file Check the current configuration informat...

Страница 82: ...ce 5120 dev sda1 0 The following examples show the output of the pvs and lvs commands with the P argument specified when a leg of a mirrored logical volume has failed root link 08 vgs a o devices P Pa...

Страница 83: ...y created Physical volume dev sde2 successfully created Physical volume dev sdf1 successfully created Physical volume dev sdf2 successfully created Physical volume dev sdg1 successfully created Physic...

Страница 84: ...device is now a linear device Because of the failed disk I O errors occur root link 08 lvs a o devices dev sda1 read failed after 0 of 2048 at 0 Input output error dev sda2 read failed after 0 of 2048...

Страница 85: ...7 83 GB 67 83 GB free PV dev sdc1 VG vg lvm2 67 83 GB 67 83 GB free PV dev sdc2 VG vg lvm2 67 83 GB 67 83 GB free PV dev sdd1 VG vg lvm2 67 83 GB 67 83 GB free PV dev sdd2 VG vg lvm2 67 83 GB 67 83 GB...

Страница 86: ...shows the sort of output you may see if the metadata area is missing or corrupted root link 07 backup lvs a o devices Couldn t find device with uuid FmGRh3 zhok iVI8 7qTD S5BI MAEN NYM5Sk Couldn t fi...

Страница 87: ...version of the software that used different defaults The pvcreate command overwrites only the LVM metadata areas and does not affect the existing data areas root link 07 backup pvcreate uuid FmGRh3 z...

Страница 88: ...ical volumes in the volume group with the partial argument of the vgchange command You can remove all the logical volumes that used that physical volume from the volume group with the removemissing ar...

Страница 89: ...tents you can run the following command using the lower case l argument to use extents instead of bytes lvcreate l8780 n testlv testvg This uses all the free extents in the volume group vgs o vg_free_...

Страница 90: ...78...

Страница 91: ...can bring up this utility by typing system config lvm The LVM chapter of the Red Hat Enterprise Linux Deployment Guide provides step by step instructions for configuring an LVM logical volume using th...

Страница 92: ...80...

Страница 93: ...e activated using the Device Mapper Each logical volume is translated into a mapped device Each segment translates into a line in the mapping table that describes the device The Device Mapper provides...

Страница 94: ...82...

Страница 95: ...ration file read by the tools etc lvm lvm_hosttag conf For each host tag an extra configuration file is read if it exists lvm_hosttag conf If that file defines new tags then further configuration file...

Страница 96: ...prefixed with either an a for accept or r for reject The first expression found to match a device name determines if the device will be accepted or rejected ignored Devices that don t match any patte...

Страница 97: ...tions types fd 16 If sysfs is mounted 2 6 kernels restrict device scanning to the block devices it believes are valid 1 enables 0 disables sysfs_scan 1 By default LVM2 will ignore devices used as comp...

Страница 98: ...kups and archiving In LVM2 when we talk about a backup we mean making a copy of the metadata for the current system The archive contains old metadata configurations Backups are stored in a human reada...

Страница 99: ...uld suppress the error messages activation 1 If we can t communicate with device mapper should we try running the LVM1 tools This option only applies to 2 4 kernels and is provided to help you switch...

Страница 100: ...1 metadata was compiled as a shared library use format_libraries liblvm2format1 so Full pathnames can be given Search this directory first for shared libraries library_dir lib The external locking lib...

Страница 101: ...cement for the failed device Using this policy for the log is fast and maintains the ability to remember sync state through crashes reboots Using this policy for a mirror device is slow as it requires...

Страница 102: ...eferably on different non LV filesystems and with no other on disk metadata pvmetadatacopies 0 Or this can be in addition to on disk metadata areas The feature was originally added to simplify testing...

Страница 103: ...e database tag lvs database 1 Adding and Removing Object Tags To add or delete tags from physical volumes use the addtag or deltag option of the pvchange command To add or delete tags from volume grou...

Страница 104: ...in the metadata on that host activation volume_list vg1 lvol0 database There is a special match that causes a match only if any metadata tag matches any host tag on that machine As another example co...

Страница 105: ...m If you intend to split the volume group in the future every volume group needs at least one metadata copy The core metadata is stored in ASCII A metadata area is a circular buffer New metadata is ap...

Страница 106: ...to determine the block device containing it Any properties such as whether the physical volume is allocatable The offset to the start of the first extent within the physical volume in sectors The numb...

Страница 107: ...abytes pe_start 384 pe_count 4390 17 1484 Gigabytes pv1 id ZHEZJW MR64 D3QM Rv7V Hxsa zU24 wztY19 device dev sdb Hint only status ALLOCATABLE dev_size 35964301 17 1491 Gigabytes pe_start 384 pe_count...

Страница 108: ...E segment_count 2 segment1 start_extent 0 extent_count 1280 5 Gigabytes type striped stripe_count 1 linear stripes pv0 0 segment2 start_extent 1280 extent_count 1280 5 Gigabytes type striped stripe_co...

Страница 109: ...60 volume groups 26 creating LVM volumes overview 17 D data relocation online 45 deactivating volume groups 30 exclusive on one node 30 local node only 30 device numbers major 38 minor 38 persistent 3...

Страница 110: ...tion 23 physical volume definition 7 volume group definition 9 LVM1 2 LVM2 2 lvmdiskscan command 23 lvreduce command 38 43 lvremove command 39 lvrename command 39 lvs command 47 53 display arguments 5...

Страница 111: ...owing 41 T troubleshooting 69 U units command line 21 V verbose output 21 vgcfbackup command 31 vgcfrestore command 31 vgchange command 29 vgcreate command 26 vgdisplay command 28 vgexport command 32...

Страница 112: ...100...

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