L’utilisation de la commande vxassist pour les personnes qui utilise
VxVM.
 

Le site est :

http://www.adminschoice.com/

Page officielle :

http://www.adminschoice.com/docs/vxassist_P.htm

vxassist

General
1. Creating a Volume 
 1.1 Creating a Concatenated Volume

 1.2 Creating a Striped Volume

 1.3 Creating a RAID-5 Volume

2. Extending a Volume
 2.1 Extending a volume up to certain length, 

  2.2 Extending by a Given Length
3. Shrinking a Volume

 3.1 Shrinking to a Given Length
 3.2 Shrinking by a Given Length
4. Removing a Volume
5. Mirroring a Volume
  5.1 Creating & Mirroring a New Volume
 5.2 Mirroring an Existing Volume
 5.3 Mirroring All Volumes
6. Removing a Mirror
7. Adding a RAID-5 Log
8. Adding a DRL Log
9. Removing a RAID-5 Log

10.Preparing a Volume for Online Backup
11.Displaying Volume Configuration Information

 

General 

The vxassist utility in Veritas Volume Manager is used to create volumes, add mirrors and logs to existing volumes, extend and shrink existing volumes, provides for the migration of data from a specified set of disks, and provides facilities for the on-line backup of existing volumes.

The default behavior of vxassist is to create volumes in the rootdg diskgroup if diskgroup is not specified . The default length is taken as number of blocks but this can be specified in Kilobytes orMegabytes or Gigabytes.

Commonly used options are given below (See man vxassist for complete list of supported options)

-g for specifying diskgroups

-b for background operation

-d file containing defaults for vxassist if not specified /etc/default/vxassist is used

 

Keywords used are make , mirror , move , growto ,growby ,shrintto ,shirnkby ,snapstart , snapshot ,snapwait

 

Attributes specify volumes layout disks controllar to include exclude etc

Default rootdg disk group.

Block Device Node /dev/vx/dsk/volume_name

Raw Device Node /dev/vx/rdsk/volume_name

Other DiskGroups

Block Device Node /dev/vx/dsk/diskgroup_name/volume_name

Raw Device Node /dev/vx/rdsk/diskgroup_name/volume_name

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By default, vxassist creates a concatenated volume using the space available
on a disk or on the number of disks in a diskgroup if the volume size specified
is more then the one available on a single disk.

Disks can be specified from a diskgroup for a volume group but if not
mentioned available disks are selected by the volume manager.

· vxassist make volume_name
volume_length

To create a new volume appvol of 100 MB in the default disk group rootdg with available disks :

· #vxassist make appvol 100m

To create the volume appvol of 100MB on disk03

· #vxassist make appvol 100m
disk03

 

A striped volume contains at least one plex that consists of two or more
subdisks located on two or more physical disks.

Command Syntax :

· vxassist make volume_name
length layout=stripe

To create a striped volume appvol2 with the default stripe unit size on the
default number of disks

· #vxassist make appvol2
100m layout=stripe

· #vxassist make appvol2 100m
layout=stripe disk04 disk05 disk06

A RAID-5 volume contains a RAID-5 plex that consists of two or more subdisks
located on two or more physical disks. Only one RAID-5 plex can exist per
volume. A RAID-5 volume may also contain one or more RAID-5 log plexes, which
are used to log information about data and parity being written to the volume.

· vxassist make volume_name
length layout=raid5

· #vxassist make appvol4 100m
layout=raid5.

Caution : If you plan to use volume size change (grow or shrink ) on a
volume with data make sure you have the good backup of the volume available
before carrying out such operation .

· vxassist growto volume_name
length

· #vxassist growto vol3 8000

· vxassist growby volume_name
length

· #vxassist growby volapp 1000

Caution - Do not shrink a volume below the size of the file system. If
you have a VxFS file system, you can shrink the file system and then shrink the
volume. If you do not shrink the file system first, you risk unrecoverable data
loss.

Always make sure you have a good backup of the data volume to be shirnked.

Shrink a volume to a specific length as follows :

· vxassist shrinkto
volume_name length

Make sure you do not shrink the volume below the current size of the file
system or database using the volume. This command can be safely used on empty
volumes.

To shrink volcat to 1300 sectors, type :

· #vxassist shrinkto volcat
1300

Shrink a volume by a specific length as follows :

· vxassist shrinkby
volume_name length

To shrink volcat by 8000 sectors, type :

· #vxassist shrinkby volapp2
8000

Removing a volume requires removing all references to the volumes to be
removed like unmounting the volume if mounted and removing its reference from
/etc/vfstab .

An active volume has to be stopped first to stop all the activities to the
volume only then it can be removed 

· vxvol stop volume_name

· #vxvol stop appvol1

· vxedit -rf rm volume_name

· #vxedit -rf rm appvol11

Mirroring allow data to be written simultaneously to two disks so that in
case of failure of one disk data is available from the other mirrored disk. Boot
disks can be mirriored to provide alternate booting disk .

· vxassist make volume_name
length layout=mirror

· #vxassist make appvol22 100m
layout=mirror

· #vxassist make volume_name
length layout=mirror,log

· vxassist mirror volume_name

· #vxassist mirror vol44

To mirror all existing volumes to available disk space

· /etc/vx/bin/vxmirror -a

Removing a mirror involves first dissociating the plex from its volume and
then removing the plex and any associated subdisks completely.The last valid
mirror plex associated with a volume cannot be removed.

Dissociate and remove the plex from its volume as follows :

· vxplex -o rm dis plex_name

vxprint -h shows the volume and associated plexes :

To disassociate and remove volmir-02 from volmir, type :

· #vxplex -o rm dis volm-02

The output of vxprint -h for volm now shows volume volm with only one plex: :

RAID-5 log plexes are used to log information about data and parity being
written to the raid volume. A log plex is created for the volume by default when
a raid volume is created but additional ones can be added by following command .

· vxassist addlog
name_of_raid5_vol

To put Dirty Region Logging into effect for a volume, a log subdisk must be
added to that volume and the volume must be mirrored. Only one log subdisk can
exist per plex.

The following example creates a log for the mirrored volume vol03 :

· #vxassist addlog vol03

When vxassist is used to add a log subdisk to a volume, a log plex is also
created to contain the log subdisk, by default.

Once created, the plex containing a log subdisk can be treated as a regular
plex. Data subdisks can be added to the log plex. The log plex and log subdisk
can be removed using the same procedures used to remove ordinary plexes and
subdisks.

Removing a RAID-5 log involves first dissociating the log from its volume and
then removing the log and any associated subdisks completely.

Dissociate the log from its volume as follows :

· #vxplex -o rm dis
plex_name

To identify the log plex, use the command :

· vxprint -ht
raid5_volume_name

To disassociate the log plex volrd-02 from volrd, type :

· #vxplex -o rm dis volrd-02

 

Disk group : rootdg TY NAME ASSOC
KSTATE LENGTH PLOFFS STATE TUTIL0 PUTIL0 v volrd raid5 ENABLED 32 - ACTIVE - -
pl volrd-01 volrd ENABLED 32 - ACTIVE - - sd disk01-02 volrd-01 - 32 0 - - - sd
disk02-03 volrd-01 - 32 0 - - -

Volume manager provides an easy way to take backup of the online data by
creating an offline snapshot mirror of the volume .

The vxassist snapstart operation creates a write-only backup mirror, which is
attached to and synchronized with the volume to be backed up and later detached
and made offline by vxassist snapshot command . The snapshot volume can
be used by backup utilities while the original volume continues to be available
for applications and users.

The volume backup method described here does not apply to RAID-5 volumes.

Backing up a volume with vxassist involves the following procedure

snapstart starts creating a online snapshot mirror of the volume using the
available disk space . The snapshot is completed with vxassist snapshot command
when offline snapshot volume is created with a userdefined name .

• vxassist snapstart volume_name

• #vxassist snapstart vol8

vxassist snapshot volume_name new_volume_name

To create a snapshot volume of vol8, type :

#vxassist snapshot vol8 snapvol8

You can now back up the snapshot volume by whatever means you prefer. To
avoid wasting space, you can then remove the snapshot volume, which occupies as
much space as the original volume

The vxprint command can be used to display information about how a volume is
configured.

Display the volume, mirror, and subdisk record information for all volumes as
follows :

  Disk group: rootdg  
  
  DG  NAME        NCONFIG    NLOG      MINORS     GROUP-ID  
  DM  NAME        DEVICE     TYPE      PRIVLEN    PUBLEN     STATE  
  V   NAME        USETYPE    KSTATE    STATE      LENGTH     READPOL      PREFPLEX  
  PL  NAME        VOLUME     KSTATE    STATE      LENGTH     LAYOUT       NCOL/WID MODE  
  SD  NAME        PLEX       DISK      DISKOFFS LENGTH       [COL/]OFF    DEVICE     MODE  
  
  dg  rootdg      759096729.1025.tweety  
  
  dm  disk10      c1t0d0s2 sliced      559        1044400     -  
  dm  disk20      c2t0d0s2 sliced      559        1044400     -  
  
  v   pubs        fsgen      ENABLED ACTIVE       2288       SELECT       -  
  pl  pubs-01     pubs       ENABLED ACTIVE       2288       CONCAT       -          RW  
  sd  disk10-01 pubs-01      disk10    0          2288       0            c0t0d0     ENA  
  
  v   vol8      fsgen      ENABLED ACTIVE       20480      SELECT       -  
  pl  vol8-01   vol8       ENABLED ACTIVE       20480      CONCAT       -          RW  
  sd  disk10-02 vol8-0 disk10        2288       20480      0            c0t1d0     ENA  

where dg is a disk group, dm is a disk, v is a volume, pl is a plex, and sd
is a subdisk. The top few lines indicate the headers that match each type of
output line that follows. Each volume is listed along with its associated
plex(es) and subdisk(s).

Display volume-related information for a specific volume as follows :

#vxprint -t volume_name

To display information about vol8, type :

#vxprint -t vol8