Use the chvdisk command
to modify the properties of a volume, such as the disk name, I/O
governing rate, or unit number. You can
also change Easy Tier ® settings.
Syntax
chvdisk
{
-namenew_name_arg | [ -cache
{ readwrite
| readonly
| none } [ -force ] ] | [ -rate
throttle_rate [-unitmb]
] | [ -udid vdisk_udid
] | { [ -warning
disk_size [ -unit
{ b | kb | mb
| gb | tb | pb } ]
] | [ disk_size_percentage
% ] } | [ {
[ -copyid ]
} ] | [ -autoexpand
{ on | off
} [ { [ -copyid ]
} ] ] | [ -primary
copy_id ] | [ -syncraterate ] | [ -easytier { on | off } [ -copy
id ] ] | [ -mirrorwritepriority { latency | redundancy } ]
} { vdisk_name
| vdisk_id }
Parameters
- -namenew_name_arg
- (Optional) Specifies a new name to assign to the volume. You cannot
use this parameter with the -rate or -udid parameters. This parameter is required if you do
not use the -rate or -udid parameters.
Note: Do not use this parameter with file system volumes.
- -cachereadwrite
| readonly | none
- (Optional) Specifies
the caching options for the volume. Valid entries are:
- readwrite to enable the cache for the volume
- readonly to disable
write caching while allowing read caching for a volume
- none to disable the cache mode for the volume
The default is
readwrite.
Remember: If you do not specify the -cache parameter, the default value (readwrite) is used.
- -force
- (Optional) The force parameter can
only be used for changing the
caching mode. Use the force parameter with the cache parameter
to specify that you want the system to change the cache mode of the
volume 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, the contents of
the cache are discarded and the volume might be corrupted by the loss
of the cached data. This could occur if the system is able to destage
all write data from the cache or not. The force parameter should be used with caution.
Important: Using the force parameter might result in a loss
of access. Use it only under the direction of your product support
information.
- -ratethrottle_rate-unitmb
- (Optional)
Specifies the I/O governing rate for the volume, which caps the amount
of I/O that is accepted. The default throttle_rate units are I/Os. By default the throttle_rate is disabled. To change the throttle_rate units
to megabytes per second (MBps), specify the -unitmb parameter. The governing rate for a volume can be specified by I/Os
or by MBps, but not both. However, you can set the rate to I/Os for
some volumes and to MBps for others. When the Input/Output
Operations Per Second (IOPS) limit is configured on a volume, and
it is smaller than 100 IOPS, the throttling logic rounds it to 100
IOPS. Even if throttle is set to a value smaller than 100 IOPs, the
actual throttling occurs at 100 IOPs.
Note: To disable
the throttling on a specific volume, set the throttle_rate value to zero.
You cannot use this parameter with
the -name or -udid parameters.
- -udidvdisk_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 parameters.
- -warningdisk_size
| disk_size_percentage%
- (Optional)
Generates a warning when the used disk capacity on the thin-provisioned
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 volume size. To disable warnings,
specify 0 or 0%.
- -unitb | kb | mb
| gb | tb | pb
- (Optional) Specifies
the data units to use for the -warningdisk_size parameter. The default unit value is MB.
- -autoexpandon | off
- (Optional) Specifies whether thin-provisioned volume copies automatically expand their real capacities by allocating
new extents from their managed disk group. To use this parameter,
the volume must be thin-provisioned.
- -copyid
- (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 volume is mirrored and only one volume copy is thin-provisioned. If both copies are thin-provisioned
and the -copy parameter is not specified, the
specified -autoexpand or -warning parameter is set on both copies.
- -primarycopy_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. You cannot change the volume's primary
copy if that primary copy has its autodelete flag
is set to yes (on).
Important: You cannot use this parameter with a
volume that is fast formatting.
- -syncraterate
- (Optional) Specifies the copy synchronization rate.
A value of zero (0) prevents synchronization.
The default value is 50. See Table 1 for the
supported -syncrate values and their corresponding
rates.
- -easytieron | off
- (Optional) Enables or disables
the Easy Tier function.
- -mirrorwriteprioritylatency | redundancy
- (Optional) Specifies
how to configure the mirror write algorithm priority. A change to
the mirror write priority is reflected in the volume's view immediately
and in the volume's behavior after all prior input and output (I/O)
completes.
- Choosing latency means a copy that is slow
to respond to a write I/O becomes unsynchronized, and the write I/O
completes if the other copy successfully writes the data
- Choosing redundancy means a copy that is slow
to respond to a write I/O synchronizes completion of the write I/O
with the completion of the slower I/O in order to maintain synchronization.
- If not specified, the current value is unchanged.
- vdisk_name | vdisk_id
- (Required) Specifies the volume to modify, either by ID or by name.
Description
The chvdisk command
modifies a single property of a volume. To change the volume name and modify the
synchronization rate, for example, you must issue the command twice.
If the volume is offline, use
one of the recovervdisk command to recover the volume and bring it back online.
Important: To change the
caching I/O group for a volume or preferred node, use the movevdisk command.
You can specify a new name
or label. You can use the new name subsequently to refer to the volume.
You can set a limit on the amount of I/O transactions
that is accepted for this volume.
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 volume is created.
Attention: All capacities, including
changes, must be in multiples of 512 bytes. An error occurs if you
specify a capacity that is not a multiple of 512, which can only happen
when byte units (-b) are used. The default capacity is in MB.
When the volume is created, there
is no throttling applied to it. Using the -rate parameter can change this. To change the volume back to an unthrottled state, specify 0 (zero) with
the -rate parameter.
This table provides the relationship of the rate value to
the data copied per second.
Table 1. Relationship between the rate value and the data copied per
second
| User-specified rate attribute value |
Data copied/second |
| 1 - 10 |
128 KB |
| 11 - 20 |
256 KB |
| 21 - 30 |
512 KB |
| 31 - 40 |
1 MB |
| 41 - 50 |
2 MB |
| 51 - 60 |
4 MB |
| 61 - 70 |
8 MB |
| 71 - 80 |
16 MB |
| 81 - 90 |
32 MB |
| 91 - 100 |
64 MB |
An invocation example
chvdisk -rate 2040 1
The resulting
output:
No feedback
An invocation example
chvdisk -cache readonly 1
The resulting output:
No feedback