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How to determine free space in a disk group using the vxassist maxsize and maxgrow commands

Article: 100000497
Last Published: 2023-10-14
Ratings: 10 1
Product(s): InfoScale & Storage Foundation

Description


The article describes how to determine the free space in a Veritas Volume Manager (VxVM) disk group using the vxassist maxsize and maxgrow commands.
 

There are several ways to determine both the contiguous and total free space that is available in a disk group. The output is in  512 byte sectors by default (except on HP-UX systems, which uses 1024 byte segments).

From the command line:

1. To determine regions of total free space on all disks across all imported disk groups:
 
# vxdg free

2. To determine regions of total free space for a specific imported disk group, type:
 
# vxdg -g <disk group> free

When querying the system to determine how much space will be available for a particular volume, it is crucial you specify the volume layout for the type of volume you are going to create, e.g.


Using the following disk group " tdg" (Each LUN is 2G in size):
 
# vxdg -g tdg free​​​​​​​
DEVICE      TYPE            DISK        GROUP        STATUS
sdb          auto:sliced    disk01      tdg          online
sdc          auto:sliced    disk02      tdg          online
sdd          auto:sliced    disk03      tdg          online

The vxassist " maxsize" argument helps determine the maximum volume size that can be created for specified diskgroup " tdg":
 
# vxassist -g tdg maxsize
Maximum volume size: 12472320(6090Mb)

NOTE: The maxsize operation will use the default concatenated (concat) layout by default to establish the maximum volume size.

To indicate a different volume layout use the " layout" parameter:
 
# vxassist -g tdg maxsize layout=striped
Maximum volumesize: 8314880 (4060Mb)

The available size has changed for the above example from 6090Mb (concat layout) to 4060Mb for the striped volume layout. The default stripe column count is 2 columns, when no column count is specified.

The " maxgrow" command can be used to determine how much space can be added to an existing volume.  This command respects volume layout device restrictions.

Example Section:
 
# vxassist -g tdg make tvol 1000M layout=striped ncols=3

# vxprint -htqg tdg


dgtdg          default      default  0        1262975382.14.therat

dmdisk01      sdb          auto     2074    4158112  -
dmdisk02      sdc          auto     2074    4158112  -
dmdisk03      sdd          auto     2074    4158112  -

v  tvol        -            ENABLED  ACTIVE  2048000  SELECT    tvol-01  fsgen
pltvol-01      tvol        ENABLED  ACTIVE  2048256  STRIPE    3/128    RW
sddisk01-01    tvol-01      disk01  0        682752   0/0      sdb      ENA
sddisk02-01    tvol-01      disk02  0        682752   1/0      sdc      ENA
sddisk03-01    tvol-01      disk03  0        682752   2/0      sdd      ENA


To determine how much space is left available for a concat volume (total free space in disk group):
 
# vxassist -g tdg maxsize
Maximum volume size: 10424320(5090Mb)


To determine how much space is left available for a new 2 column stripe volume:
 
# vxassist -g tdg maxsize layout=striped ncols=2
Maximum volume size: 6948864(3393Mb)


To determine how much the existing volume ' tvol' can be grown:
 
# vxassist -g tdg maxgrow tvol​​​​​​​
Volume tvol can be extended by10424320 to: 12472320 (6090Mb) ​​​​​​​

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