The chvdisk command modifies the properties of a virtual disk, such as the disk name, I/O group, I/O governing rate, or unit number.
Syntax
>>- svctask -- -- chvdisk -- --+-------------------------+------> '- -name -- new_name_arg -' >--+---------------------------------------------+--------------> +- -iogrp --+- io_group_id ---+--+----------+-+ | '- io_group_name -' '- -force -' | '- -cache --+-readwrite-+--+----------+-------' '-none------' '- -force -' >--+--------------------------+--+--------------------------+---> '- -node --+- node_id ---+-' '- -rate -- throttle_rate -' '- node_name -' >--+-----------+--+-------------------------+-- ----------------> '- -unitmb -' '- -udid -- vdisk_udid -' >--+--------------------------------------------------+---------> '- -warning --disk_size |--disk_size_percentage--%-' >--+-------------------+--+-------------------------+-----------> '- -unit --+- b --+-' '- -autoexpand --on | off-' +- kb -+ +- mb -+ +- gb -+ +- tb -+ '- pb -' >--+--------------+--+----------------------+-------------------> '- -copy-- id -' '- -primary-- copy_id -' >--+------------------------------+--+- vdisk_name -+---------->< '- -syncrate-- percentage_arg -' '- vdisk_id ---'
Parameters
- -name new_name_arg
- (Optional) Specifies a new name to assign to the virtual disk. You cannot use this parameter with the -iogrp, -rate, -node, or -udid parameters. This parameter is required if you do not use the -iogrp, -rate, or -udid parameter.
- -iogrp io_group_id | io_group_name
- (Optional) Specifies a new I/O group to move the virtual disk
to, by I/O group ID or I/O group name. You can use the -node parameter with the -iogrp parameter to
specify a preferred node for the specified VDisk.Notes:
- If the VDisk has a mapping to any hosts, it is not possible to move the VDisk to an I/O group, unless all of those hosts are associated with the new I/O group.
- This parameter can fail if there is not enough space to allocate bitmaps for a mirrored VDisk in the target I/O group.
- This parameter can fail if any copy is not synchronized. The -force parameter can be used to force the move, but this resynchronizes the VDisk.
- If the VDisk is offline, use one of the recovervdisk commands to recover the VDisk and bring it back online. Beginning with SAN Volume Controller version 4.3.1, use of the recovery I/O group is not required.
- -cache readwrite | none
- (Optional) Specifies the caching options for the VDisk. Valid entries are readwrite, to enable the cache for the VDisk, or none, to disable the cache mode for the VDisk.
- -force
- (Optional) The force parameter
can only be used for changing the I/O group of a VDisk or the caching
mode. Use the force parameter with the iogrp parameter
to force the VDisk to be removed from an I/O group. Use the force parameter
with the cache parameter to specify that you
want the system to change the cache mode of the VDisk even if the
I/O group is offline. This option overrides the cache flush mechanism.Attention:
- If the force parameter is used for changing the caching mode or I/O group of a VDisk, the contents of the cache are discarded and the VDisk might be corrupted by the loss of the cached data. This could occur if the cluster is able to destage all write data from the cache or not. The force parameter should be used with caution.
- If the force parameter is used to move a VDisk that has out-of-sync copies, a full resynchronization is required.
- -rate throttle_rate [-unitmb]
- (Optional) Specifies the I/O governing rate for the VDisk, which caps the amount of I/O that is accepted. The default throttle_rate units are I/Os. To change the throttle_rate units to megabytes per second (MBps), specify the -unitmb parameter. The governing rate for a virtual disk can be specified by I/Os or by MBps, but not both. However, you can set the rate to I/Os for some virtual disks and to MBps for others.
You cannot use this parameter with the -name, -iogrp, -node, or -udid parameters.
- -udid vdisk_udid
- (Optional) Specifies the unit number (udid) for the disk. The vdisk_udid is an identifier that is required to support OpenVMS hosts; no other systems use this parameter. Valid options are a decimal number from 0 to 32 767 or a hexadecimal number from 0 to 0x7FFF. A hexadecimal number must be preceded by 0x (for example, 0x1234). If you do not use the -udid parameter, the default udid is 0.
You cannot use this parameter with the -name, -iogrp, -node, or -rate parameters.
- -warning disk_size | disk_size_percentage%
- (Optional) Generates a warning when the used disk capacity on the space-efficient copy first exceeds the specified threshold. You can specify a disk_size integer, which defaults to MBs unless the -unit parameter is specified; or you can specify a disk_size%, which is a percentage of the virtual disk size. To disable warnings, specify 0 or 0%.
- -unit b | kb | mb | gb | tb | pb
- (Optional) Specifies the data units to use for the -warning disk_size parameter.
- -autoexpand on | off
- (Optional) Specifies whether space-efficient VDisk copies automatically expand their real capacities by allocating new extents from their managed disk group. To use this parameter, the VDisk must be space-efficient.
- -copy id
- (Optional) Specifies the copy to apply the changes to. You must specify this parameter with the -autoexpand or -warning parameter. The -copy parameter is required if the specified VDisk is mirrored and only one VDisk copy is space-efficient. If both copies are space-efficient and the -copy parameter is not specified, the specified -autoexpand or -warning parameter is set on both copies.
- -primary copy_id
- (Optional) Specifies the primary copy. Changing the primary copy only takes effect when the new primary copy is online and synchronized. If the new primary is online and synchronized when the command is issued, the change takes effect immediately.
- -syncrate percentage
- (Optional) Specifies the copy synchronization rate, as a percentage of the peak synchronization rate. A value of zero (0) prevents synchronization.
- -node node_id | node_name
- (Optional) Specifies a preferred node for the specified VDisk. When using this parameter, you must also specify the -iogrp parameter. You cannot use this parameter with the -name, -rate, or -udid parameters.
- vdisk_name | vdisk_id
- (Required) Specifies the virtual disk to modify, either by ID or by name.
Description
The chvdisk command modifies a single property of a virtual disk (VDisk). To change the VDisk name and modify the I/O group, for example, you must issue the command twice.
You can specify a new name or label. You can use the new name subsequently to refer to the virtual disk. To specify a preferred node for the VDisk, use the -node node_id | node_name parameter.
You can change the I/O group with which this virtual disk is associated. However, to change the I/O group, you must first flush the cache within the nodes in the current I/O group to ensure that all data is written to disk. Ensure that you suspend I/O operations at the host level before you perform this operation.
- Do not move a VDisk to an offline I/O group under any circumstance. To avoid any data loss, you must ensure that the I/O group is online before you move the VDisks.
- Do not move an offline VDisk to the recovery I/O group. Beginning with SAN Volume Controller version 4.3.1, use of the recovery I/O group is not required. Instead, use one of the recovervdisk commands to recover the VDisk and bring it back online.
You can set a limit on the amount of I/O transactions that is accepted for this virtual disk. It is set in terms of I/Os per second or MBs per second. By default, no I/O governing rate is set when a virtual disk is created.
When the virtual disk is created, there is no throttling applied to it. Using the -rate parameter can change this. To change the virtual disk back to an unthrottled state, specify 0 (zero) with the -rate parameter.
You can migrate a VDisk to a new I/O group to manually balance the workload across the nodes in the cluster. You might end up with a pair of nodes that are overworked and another pair that are underworked. Use the following procedure to migrate a single VDisk to a new I/O group. Repeat for other VDisks as required.
Ensure that when you migrate a VDisk to a new I/O group, you quiesce all I/O operations for the VDisk. Determine the hosts that are using this VDisk. Stop and delete any FlashCopy® mappings or Metro or Global Mirror relationships that use this VDisk. To check if the VDisk is part of a relationship or mapping, issue the svcinfo lsvdisk vdiskname | id command, where vdiskname | id is the name or ID of the VDisk.
svctask chvdisk -iogrp newiogrpname|id vdiskname|id
Follow the procedure to discover the new vpaths and to check that each vpath is presenting the correct number of paths. Refer to Multipath Subsystem Device Driver (SDD) documentation for details on how to dynamically reconfigure SDD for the given host operating system.An invocation example
svctask chvdisk -rate 2040 -unitmb 6
The resulting output
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