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HP-UX Reference > Vvgchange(1M)HP-UX 11i Version 2: December 2007 Update |
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NAMEvgchange — set LVM volume group availability SYNOPSISActivate volume group/usr/sbin/vgchange -a availability [-l] [-p] [-q quorum] [-s] [-P resync_daemon_count] [vg_name...] Assign to high availability cluster and mark volume group sharable/usr/sbin/vgchange -c cluster -S sharable vg_name RemarksMC/ServiceGuard cluster operations require the installation of the optional MC/ServiceGuard software, which is not included in the standard HP-UX operating system. Mirrored disk operations require the installation of the optional HP MirrorDisk/UX software, which is not included in the standard HP-UX operating system. DESCRIPTIONThe vgchange command with the -a option activates or deactivates one or more volume groups. When the -a option is used together with the -x option, the vgchange command allows cross-activation of a sharable volume group to the desired activation mode in a high availability cluster. The vgchange command with the -c option controls the membership of one or more volume groups in a high availability cluster. The vgchange command with the -c and -S options control the membership of a volume group and mark it sharable. The vgchange command without the -P resync_daemon_count option (default) will spawn one nomwcsyncd process for each NOMWC/NONE volume group being activated. This may create a lot of nomwcsyncd processes running concurrently when it activates a large number of NOMWC/NONE volume groups and overload. The -P resync_daemon_count option provides a way to control the number of concurrent nomwcsyncd processes. The count is an advisory number and a different count might be chosen internally if load balance or other reason is needed. When specified, there are up to resync_daemon_count + 1 nomwcsyncd processes; one of them is the controlling processing to spawn others. -P 0 will use the system default (currently defined to be 4). vg_name must be defined as a volume group in the file /etc/lvmtab. If vg_name is omitted, all volume groups defined in /etc/lvmtab are affected, when the -x option is not specified. High Availability Cluster OverviewVolume groups can be defined on disk volumes that are accessible by more than one system in a high availability cluster. This situation has a high potential for data corruption unless higher level cluster software services are used to coordinate shared access to the same volume group by all systems. A volume group can be marked as part of a cluster. When such a group is activated in exclusive mode, it can be accessed for exclusive read-write activity by only one of the systems at a time; the other systems can have read-only access to the data. When the volume group is marked as sharable, it may be activated in shared mode for read-write access by all the nodes in the cluster. The configuration of a shared volume group can be changed only if it is activated in exclusive mode. Cross-activation between shared and exclusive modes of shared volume groups is possible with the -x option to vgchange. Options and Argumentsvgchange recognizes the following options and arguments:
Mirrored Disk ActivationWhen the optional HP MirrorDisk/UX software is running and a volume group is activated, LVM performs the necessary mirror consistency recovery for each logical volume in the volume group based on the state of Mirror Write Cache and Mirror Consistency Recovery (see the Consistency Recovery section of lvdisplay(1M)). In a non-shared environment, LVM supports MWC, NOMWC and the NONE recovery. But in shared environment, LVM only supports NOMWC and the NONE recovery.
Next, mirror synchronization refreshes stale mirror copies by copying data from a nonstale copy. If the -s option is specified on the command line, mirror synchronization does not occur. However, for those logical volumes that have Mirror Write Cache turned off, mirror synchronization is done independently of whether the -s option appears on the command line. General ActivationIf vgchange cannot access a physical volume, it lists the volume's status as missing. If too many physical volumes in the volume group are missing, vgchange reports that the group does not have a quorum and cannot be activated. The lack of a quorum can be overridden with the -q n option. EXTERNAL INFLUENCESEnvironment VariablesLANG determines the language in which messages are displayed. If LANG is not specified or is null, it defaults to "C" (see lang(5)). If any internationalization variable contains an invalid setting, all internationalization variables default to "C" (see environ(5)). EXAMPLESActivate volume group /dev/vg03: vgchange -a y /dev/vg03 Deactivate volume group /dev/vg03: vgchange -a n /dev/vg03 Activate volume group /dev/vg03 without synchronizing extents that are not current on logical volumes that have Mirror Write Cache turned on: vgchange -a y -s /dev/vg03 Exclusive ActivationSet up volume group /dev/vg03 for use in a high availability cluster: vgchange -a n /dev/vg03 # Deactivate volume group vgchange -c y /dev/vg03 # Enable volume group for HA cluster vgchange -c y -S y /dev/vg03 # Enable volume group for HA cluster and mark as sharable vgchange -a e /dev/vg03 # Activate volume group in exclusive mode vgchange -a s /dev/vg03 # Activate volume group in shared mode Activate all volume groups; activate those that are marked for membership in a high availability cluster in shared mode: vgchange -a y Activate all volumes that are marked for membership in a high availability cluster in exclusive mode: vgchange -a e Cross ActivationSet up volume group /dev/sh_vg for use in a high availability cluster. To make configuration changes, to a volume group activated in shared mode, deactivate the volume group by executing the following command on each cluster node except one: vgchange -a n sh_vg On the single node, where the volume group is active:
WARNINGSOrdinary OperationIn ordinary operation (that is, without the optional high availability software), it is possible to activate a volume group for read-write access from more than one physically connected system, leading to a high potential for data corruption. Therefore, if access is desired from more than one system to a single volume group, it is important that only one system activate the volume group for read-write access; the other systems can use read-only access. There is no problem if all systems activate the volume group for read-only access. Furthermore, volume group information is only read from the disks during volume group activation. Dynamic changes to the volume group such as the following are not propagated to other systems sharing the volume group:
Because of these limitations, when sharing volume groups between systems, it is recommended that logical volumes be accessed only by one system at a time. If logical volumes must be accessed simultaneously, the logical volumes should not be mirrored and should not have bad-block relocation turned on, or all systems should use read-only access to the logical volumes. In order to activate a logical volume greater than 2 terabytes, the kernel must be updated to support this feature, and the corresponding feature enabling patch must be installed. In order to activate a striped and mirrored logical volume, the kernel must be updated to support this feature, and the corresponding feature enabling patch must be installed. SEE ALSOmount(1M), vgcreate(1M), vgextend(1M), vgreduce(1M), vgdisplay(1M). If MC/ServiceGuard is installed: cmcheckconf(1M), cmquerycl(1M), and Managing MC/ServiceGuard. |
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