Using the vgmove command to perform LVM Volume Group migration

Transcription

1 Using the vgmove command to perform LVM Volume Group migration Abstract... 2 Overview... 2 When do you use vgmove?... 2 Prerequisites... 2 How to use vgmove... 2 Volume group migration flow... 3 How to recover from failures... 4 Examples... 4 Migrating a volume group (vg01) that has a single disk... 4 Migrating volume group (vg01) having multiple disks and mirrored volumes... 6 LVM vgmove Messages... 8 For more information... 9 Call to action... 10

2 Abstract This white paper describes the data mobility enhancements in LVM. You can now move LVM data from an existing set of disks or DSFs to a new set of disks or DSFs without any application downtime. In addition, you can move the data within or across storage frames. This paper is intended for system administrators or operators who have experience with both HP-UX and LVM. The HP-UX 11i v3 September 2009 Update provides a new command, vgmove, for volume group mobility. The vgmove command supports migration of Version 1.0 and 2.x volume groups. This paper explains how to use the vgmove command to perform the volume group migration. Overview The vgmove command enables you to migrate data from an existing set of disks in a volume group to a new set of disks. You can perform volume group migration online only. The vgmove command is supported for both Version 1.0 and 2.0 volume groups in standalone and exclusive mode only. For Version 2.1 and greater volume groups, you can perform vgmove when a volume group is activated in shared, exclusive, or standalone mode. The volume group migration occurs with the data in place. Prior to the vgmove command, LVM supported moving of physical volumes within a volume group, but you needed to perform many configuration steps. When do you use vgmove? To migrate the volume group from one set of disks to another set of disks. When the boot disk volume group runs out of disk space for the root volume. To migrate data from a smaller storage device to a larger storage device Prerequisites Before migrating a volume group, you must meet the following prerequisites: The volume group must be activated during migration. The volume group must be not be quieseced (both write mode and read-write mode with or without timeout set). Do not activate the volume group in read-only mode. All physical volumes belonging to the volume group must be accessible. How to use vgmove 1. Take a configuration backup of the volume group using vgcfgbackup -f, as a precautionary measure. You can use this to recover the initial or original volume group configuration, if ncessary. Save this configuration backup file in a known location, other than the default location; otherwise, it might be overwritten by a configuration change done later. 2. Prepare the diskmap file to be used for volume group migration. The diskmap file specifies the list of source disks from which to move data and the list of destinations disks to which to move data. You have the option to list only a subset of the existing physical volumes in the volume group that needs to be migrated to new disks. The format of the diskmap file is as follows: source_pv_1 destination_pv_1_1 destination_pv_1_2... source_pv_2 destination_pv_2_1 destination_pv_2_2... 2

3 ... source_pv_n destination_pv_n_1 destination_pv_n_2... You can generate the diskmap file manually or automatically as follows: o Manually To move data in volume group /dev/vg01 from /dev/disk/disk100 to /dev/disk/disk101, enter: #echo /dev/disk/disk100 /dev/disk/disk101 > diskmap.txt o Automatically To move data in a volume group /dev/vg01 from /dev/disk/disk100 to /dev/disk/disk101, add the new disks to a file as follows: #echo /dev/disk/disk101 > newdisk.txt Then, generate the diskmap file as follows: #vgmove i newdisk.txt f diskmap.txt /dev/vg01 The preceding examples show only one disk. You can generate a diskmap file with multiple disks. 3. Preview the migration operation to check whether the migration can finish successfully. #vgmove p f diskmap.txt /dev/vg01 4. Make sure that all the prerequisites are met. The vgmove command reports failures if any of the prerequisites are not met. 5. Make sure that all the destination physical volumes have enough space to accommodate the source logical volumes. Note that vgmove command internally checks and fails if there is not enough space. 6. After the command completes in preview mode, execute the actual command as follows: #vgmove f diskmap.txt /dev/vg01 Volume group migration flow The following steps describe the flow of the volume group migration. The flow helps you to take necessary action in case of any unexpected failures. 1. The vgmove command checks for the availability of the source and destination disks. When it is successful, vgmove command invokes pvcreate internally. Then, it adds (using vgextend) the destination disk to the volume group, if its not already a part of the volume group. 2. After extending the volume, vgmove transfers all the logical volumes from the source disks to the destination disks using the pvmove command. While transferring the logical volumes, the vgmove command honors the allocation and mirroring policies of the extents being moved. 3. When vgmove is invoked with the preview option, the following line appears if it is successful. The diskmap.txt file has /dev/disk/disk107 and /dev/disk/disk112: # vgmove -p -f /tmp/diskmap.txt /dev/vg01 The vgmove command can be successfully run. 4. When the actual command is run following is output: # vgmove -f /tmp/diskmap.txt /dev/vg01 Physical volume "/dev/rdisk/disk112" has been successfully created. Transferring logical extents of logical volume "/dev/vg01/lvol1"... Transferring logical extents of logical volume "/dev/vg01/lvol2"... Transferring logical extents of logical volume "/dev/vg01/lvol4"... Physical volume "/dev/disk/disk107" has been successfully moved. The vgmove command completed successfully. 3

4 5. After successful migration, the destination disks are added to the /etc/lvmtab or /etc/lvmtab_p LVM configuration files. The source disks and their alternate links are removed from the LVM configuration files and the volume group. How to recover from failures When the vgmove command is interrupted manually or the system is rebooted during the volume group migration, data is not lost as long as the physical volume is. To complete the volume group migration process, invoke the vgmove command again with same syntax and arguments. After successful migration, the entries for source disks and its alternate links are removed from the LVM configuration files (/etc/lvmtab or /etc/lvmtab_p). Examples The following examples assume the volume group is activated. The vgmove command fails when run on a deactivated volume group. Migrating a volume group (vg01) that has a single disk 1. Display the configuration before the migration as follows: # vgdisplay -v /dev/vg Volume groups --- VG Name /dev/vg01 VG Write Access read/write VG Status Max LV 255 Cur LV 3 Open LV 3 Max PV 16 Cur PV 1 Act PV 1 Max PE per PV 1016 VGDA 2 PE Size (Mbytes) 32 Alloc PE 60 Total PVG 0 Total Spare PVs 0 Total Spare PVs in use 0 VG Version 1.0 VG Max Size 508g VG Max Extents Logical volumes LV Name /dev/vg01/lvol1... /syncd...lv Size (Mbytes) Allocated PE 20...Used PV 1...LV Name /dev/vg01/lvol2... /syncd...lv Size (Mbytes) Allocated PE 20...Used PV 1...LV Name /dev/vg01/lvol3... /syncd...lv Size (Mbytes) 640 4

5 ......Allocated PE 20...Used PV Physical volumes PV Name /dev/disk/disk116...pv Status Generate the diskmap file using vgmove command. 3. Add the destination disk as follows: # echo "/dev/disk/disk117" > newdisk.txt 4. Run the vgmove command with following options to autogenerate the map file: # vgmove -i /tmp/newdisk.txt -f /tmp/diskmap.txt /dev/vg01 The map file is created as follows: # cat /tmp/diskmap.txt /dev/disk/disk116 /dev/disk/disk Run the vgmove command in preview mode as follows: # vgmove -p -f /tmp/diskmap.txt /dev/vg01 The vgmove command can be successfully run. 6. Perform the actual migration after the preview mode is successful as follows: Transferring logical extents of logical volume "/dev/vg01/lvol1"... Transferring logical extents of logical volume "/dev/vg01/lvol2"... Physical volume "/dev/dsk/c5t1d1" has been successfully moved. The vgmove command completed successfully. 7. Display the configuration after the migration as follows: # vgdisplay -v /dev/vg Volume groups --- VG Name VG Write Access VG Status Max LV 255 Cur LV 3 Open LV 3 Max PV 16 Cur PV 1 Act PV 1 Max PE per PV 1016 VGDA 2 PE Size (Mbytes) 32 Alloc PE 60 Total PVG 0 Total Spare PVs 0 Total Spare PVs in use 0 VG Version 1.0 /dev/vg01 read/write VG Max Size 508g VG Max Extents Logical volumes --- LV Name /dev/vg01/lvol1 /syncd 5

6 LV Size (Mbytes) 640 Allocated PE 20 Used PV 1 LV Name /dev/vg01/lvol2 /syncd LV Size (Mbytes) 640 Allocated PE 20 Used PV 1 LV Name /dev/vg01/lvol3 /syncd LV Size (Mbytes) 640 Allocated PE 20 Used PV Physical volumes --- PV Name /dev/disk/disk117 PV Status Migrating volume group (vg01) having multiple disks and mirrored volumes 1. Display the configuration before the migration as follows: # vgdisplay -v /dev/vg Volume groups --- VG Name VG Write Access /dev/vg01 read/write VG Status Max LV 2047 Cur LV 3 Open LV 3 Max PV 2048 Cur PV 4 Act PV 4 Max PE per PV VGDA 8 PE Size (Mbytes) 32 Total PE 252 Alloc PE 180 Free PE 72 Total PVG 0 Total Spare PVs 0 Total Spare PVs in use 0 VG Version 2.1 VG Max Size 508g VG Max Extents Logical volumes --- LV Name /dev/vg01/lvol1 /syncd LV Size (Mbytes) 640 Allocated PE 40 Used PV 2 6

7 LV Name /dev/vg01/lvol2 /syncd LV Size (Mbytes) 640 Allocated PE 60 Used PV 3 LV Name /dev/vg01/lvol3 /syncd LV Size (Mbytes) 640 Allocated PE 80 Used PV Physical volumes --- PV Name /dev/disk/disk117 PV Status PV Name /dev/disk/disk116 PV Status PV Name /dev/disk/disk118 PV Status Free PE 23 PV Name /dev/disk/disk119 PV Status Free PE 43 The volume group has 4 disks and 3 logical volumes with 1, 2, 3 mirrors. 2. Generate the disk map file using the four destination disks as follows: # echo "/dev/disk/disk120" > /tmp/newdisk.txt # echo "/dev/disk/disk121" >> /tmp/newdisk.txt # echo "/dev/disk/disk122" >> /tmp/newdisk.txt # echo "/dev/disk/disk123" >> /tmp/newdisk.txt # vgmove -i /tmp/newdisk.txt -f /tmp/diskmap.txt /dev/vg01 3. Verify the diskmap.txt file as follows: # cat /tmp/diskmap.txt /dev/disk/disk117 /dev/disk/disk120 /dev/disk/disk116 /dev/disk/disk121 /dev/disk/disk118 /dev/disk/disk122 /dev/disk/disk119 /dev/disk/disk Run the vgmove command in preview mode as follows: # vgmove -p -f /tmp/diskmap.txt /dev/vg01 The vgmove command can be successfully run. 5. Perform the actual migration as follows: 7

8 # vgmove -f /tmp/diskmap.txt /dev/vg01 Physical volume "/dev/rdisk/disk120" has been successfully created. Transferring logical extents of logical volume "/dev/vg01/lvol1"... Transferring logical extents of logical volume "/dev/vg01/lvol2"... Physical volume "/dev/disk/disk117" has been successfully moved. Physical volume "/dev/rdisk/disk121" has been successfully created. Transferring logical extents of logical volume "/dev/vg01/lvol1"... Transferring logical extents of logical volume "/dev/vg01/lvol2"... Physical volume "/dev/disk/disk116" has been successfully moved. Physical volume "/dev/rdisk/disk122" has been successfully created. Transferring logical extents of logical volume "/dev/vg01/lvol2"... Physical volume "/dev/disk/disk118" has been successfully moved. Physical volume "/dev/rdisk/disk123" has been successfully created. Physical volume "/dev/disk/disk119" has been successfully moved. The vgmove command completed successfully. LVM vgmove Messages While using the vgmove command you might see status messages similar to the following: The vgmove command can be successfully run. The vgmove command was invoked in preview mode and was successful. The vgmove command completed successfully. The vgmove command sucessfully completed the volume group migration. Physical volume "/dev/rdisk/disk137" has been successfully created. When vgmove is run, it internally invokes the pvcreate command on the destination disk to create the phyiscal volume for use in the LVM volume group. If the destination disk is already part of volume group, this message is skipped. After successful creation of the phyiscal volume, vgmove internally extends the migrating volume group. If the destination disk is already part of volume group, this message is skipped. Transferring logical extents of logical volume "/dev/vg00/lvol1" The vgmove comman internally invokes the pvmove command to transfer the logical extents of a logical volume. The vgmove command migrated all the logical volumes from a source disk and invoked the vgreduce command to remove the source disk entry from the volume group. Physical volume «/dev/rdisk/disk132» is not a block special file. The diskfile or diskmap file has a character device entry. 8

9 Operation on volume group "/dev/vg01" could not succeed as physical volume "/dev/disk/disk132" cannot be accessed. If the physical volume is detached, use pvchange(1m) or vgchange(1m) to re-attach before this operation. When the source or destination disks are not, vgmove fails. Cannot move physical volume /dev/disk/disk132. Failure possibly caused by strict allocation policy. The vgmove command failed. This message is displayed when vgmove fails to migrate the volume group. This might be because the volume group has mirrored volumes and it cannot be accomadated in the destination disks. Or there are logical volumes with a strict allocation policy on source disk and the destination disks cannot honor that policy. Physical volume "/dev/disk/disk85" does not belong to volume group "/dev/vg01". The source disk does not belong to the volume group being migrated. The volume group "/dev/vg01" is not active. ly an active volume group can be extended. The volume group is in a deactivated state. A volume group must be activated to perform volume group migration. The volume group "/dev/vg01" is active in Shared Mode. Cannot perform configuration change. The vgmove command was invoked on a Version 1.0 or 2.0 shared volume groups. The vgmove command is supported on Version 2.1 or above shared volume groups. Destination disks do not contain enough space. vgmove: The vgmove command failed. The destination disk does not have enough space to migrate all the logical volumes in a source disk. You must increase the destination disk size. At least one destination physical volume must be specified. No destination disk was specified in the diskmap file. For more information To learn more about LVM and HP-UX system administration, see the following documents on the HP documentation website ( HP-UX System Administrator s Guide: Logical Volume Configuration LVM White Papers: Using the vgmodify command to perform LVM Volume Group Dynamic LUN Expansion (DLE) and Contraction (DLC) LVM Supported Limits LVM Migration from Legacy to Agile Naming Model 9

10 LVM New Features in HP-UX 11i v3 LVM line Disk Replacement (LVM OLR) LVM Volume Group Quiesce/Resume SLVM Single-Node line Reconfiguration (SLVM SNOR) When Good Disks Go Bad: Dealing with Disk Failures under LVM Using the vgversion Command to Perform LVM Volume Group Version Migration Call to action HP welcomes your input. Please give us comments about this white paper, or suggestions for LVM or related documentation, through our technical documentation feedback website: Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein. Itanium is a trademark or registered trademark of Intel Corporation or its subsidiaries in the United States and other countries. 4AA0-XXXXENW, September