How to recover a volume from vxprint -ht output after a disk group has been destroyed

Description

There will be occasions when a disk group and its associated volumes may need to be recovered.  If the volume and disk configuration information cannot be retrieved from the private region of one of the disks concerned, then the only option to recover the volume configuration so that the volume(s) can be rebuilt may be to refer to an old vxprint -th output.

Below is an example of recovering a striped volume:

# vxprint -ht -g bobdg
DG NAME        NCONFIG      NLOG    MINORS  GROUP-ID
DM NAME        DEVICE      TYPE    PRIVLEN  PUBLEN  STATE
RV NAME        RLINK_CNT    KSTATE  STATE    PRIMARY  DATAVOLS  SRL
RL NAME        RVG          KSTATE  STATE    REM_HOST REM_DG    REM_RLNK
V  NAME        RVG          KSTATE  STATE    LENGTH  READPOL  PREFPLEX UTYPE
PL NAME        VOLUME      KSTATE  STATE    LENGTH  LAYOUT    NCOL/WID MODE
SD NAME        PLEX        DISK    DISKOFFS LENGTH  [COL/]OFF DEVICE  MODE
SV NAME        PLEX        VOLNAME  NVOLLAYR LENGTH  [COL/]OFF AM/NM    MODE
DC NAME        PARENTVOL    LOGVOL
SP NAME        SNAPVOL      DCO

dg bobdg        default      default  91000    1022000899.1234.Rawfusion

dm bob01        c1t12d0s2    sliced  2393    35833392 -
dm bob02        c1t14d0s2    sliced  2393    35833392 -
dm bob03        c2t12d0s2    sliced  3199    17907200 -

v  bobvol      -            ENABLED  ACTIVE  1024000  SELECT    bobvol-01 fsgen
pl bobvol-01    bobvol      ENABLED  ACTIVE  1027200  STRIPE    3/128    RW
sd bob01-01    bobvol-01    bob01    0        342342   0/0      c1t12d0  ENA
sd bob02-01    bobvol-01    bob02    0        342342  1/0      c1t14d0  ENA   
sd bob03-01    bobvol-01    bob03    0        342400  2/0      c2t12d0  ENA   

Note: Figures in bold represent the offset and corresponding length of each subdisk that are used in the vxmake commands below.

The volume bobvol, mounted onto /test1 has a file system containing various files:

# ls -l /test1
total 32514
drwxr-xr-x  3 root    other        96 May 22 10:38 VRTS
drwxr-xr-x  3 root    other        96 May 22 10:38 VRTSlic
drwxr-xr-x  11 root    other      1024 May 22 10:39 VRTSsamba
-rw-r--r--  1 root    other    16645973 May 22 10:39 VRTSsamba.tar.Z
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvmsa
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvras
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvxfs
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvxvm
drwxr-xr-x  2 root    root          96 May 22 10:37 lost+found

# vxprint -ht -g bobdg > config.out (save the volume and disk configuration to a file for recovery later)

To simulate not being able to recover the disk group information from one of the disk's private regions, the disk group was destroyed:

# umount /test1
# vxdg destroy bobdg

From the saved output of vxprint -ht, the disk group and associated volume can be recovered.  To perform the recovery, the disk group will have to be reinitialised and the records previously in bobdg remade so that they point to the old data.  The first steps are to reinitialise the disks and rebuild the disk group. Please note that
reinitialising the disks does not interfere with data.

For disks c1t12d0s2, c1t14d0s2 and c2t12d0s2, ensure they are first reinitialised so that errors such as 'disk is already in use by another system' aren't seen:

# vxdisksetup -i c1t12d0  
# vxdisksetup -i c1t14d0
# vxdisksetup -i c2t12d0

Warning : The above vxdisksetup initializes the disks to all default settings only.  

Please be aware that the private region length has been increased in vxvm 3.2 and above.  If one is trying to restore a diskgroup that was created under vxvm 3.1.1 or lower (i.e. diskgroup version 80 or lower) and vxvm 3.2 vxdisksetup is used with the default private region length then one could lose some data, due to the overlapping of the new private and the old public regions. 

# vxdg init bobdg bob01=c1t12d0s2 bob02=c1t14d0s2 bob03=c2t12d0s2 (remake the diskgroup and assign the disks back with the same names they had originally)

Using vxmake, build the volume bobvol from the bottom up.  When making a volume from the bottom up, start by making the subdisks using the offsets and lengths from the saved vxprint -ht, then the plex(es) and then the volume itself.

# vxmake -g bobdg sd bob01-01 dm_name=bob01 dm_offset=0 len=342342
# vxmake -g bobdg sd bob02-01 dm_name=bob02 dm_offset=0 len=342342
# vxmake -g bobdg sd bob03-01 dm_name=bob03 dm_offset=0 len=342400
# vxprint -ht -g bobdg
DG NAME        NCONFIG      NLOG    MINORS  GROUP-ID
DM NAME        DEVICE      TYPE    PRIVLEN  PUBLEN  STATE
RV NAME        RLINK_CNT    KSTATE  STATE    PRIMARY  DATAVOLS  SRL
RL NAME        RVG          KSTATE  STATE    REM_HOST REM_DG    REM_RLNK
V  NAME        RVG          KSTATE  STATE    LENGTH  READPOL  PREFPLEX UTYPE
PL NAME        VOLUME      KSTATE  STATE    LENGTH  LAYOUT    NCOL/WID MODE
SD NAME        PLEX        DISK    DISKOFFS LENGTH  [COL/]OFF DEVICE  MODE
SV NAME        PLEX        VOLNAME  NVOLLAYR LENGTH  [COL/]OFF AM/NM    MODE
DC NAME        PARENTVOL    LOGVOL
SP NAME        SNAPVOL      DCO

dg bobdg        default      default  22000    1022089620.1237.Rawfusion

dm bob01        c1t12d0s2    sliced  2393    35833392 -
dm bob02        c1t14d0s2    sliced  2393    35833392 -
dm bob03        c2t12d0s2    sliced  3199    17907200 -

sd bob01-01    -            bob01    0        342342  -        c1t12d0  ENA
sd bob02-01    -            bob02    0        342342  -        c1t14d0  ENA
sd bob03-01    -            bob03    0        342400  -        c2t12d0  ENA

Create the striped plex using vxmake, specifying the use of the subdisks, layout, stripe width, columns and the correct ordering of subdisks just created.

# vxmake -g bobdg plex bobvol-01 layout=stripe ncol=3 stwidth=128 sd=bob01-01:0/0,bob02-01:1/0,bob03-01:2/0
# vxprint -ht -g bobdg (take a look at current configuration)
DG NAME        NCONFIG      NLOG    MINORS  GROUP-ID
DM NAME        DEVICE      TYPE    PRIVLEN  PUBLEN  STATE
RV NAME        RLINK_CNT    KSTATE  STATE    PRIMARY  DATAVOLS  SRL
RL NAME        RVG          KSTATE  STATE    REM_HOST REM_DG    REM_RLNK
V  NAME        RVG          KSTATE  STATE    LENGTH  READPOL  PREFPLEX UTYPE
PL NAME        VOLUME      KSTATE  STATE    LENGTH  LAYOUT    NCOL/WID MODE
SD NAME        PLEX        DISK    DISKOFFS LENGTH  [COL/]OFF DEVICE  MODE
SV NAME        PLEX        VOLNAME  NVOLLAYR LENGTH  [COL/]OFF AM/NM    MODE
DC NAME        PARENTVOL    LOGVOL
SP NAME        SNAPVOL      DCO

dg bobdg        default      default  22000    1022089620.1237.Rawfusion

dm bob01        c1t12d0s2    sliced  2393    35833392 -
dm bob02        c1t14d0s2    sliced  2393    35833392 -
dm bob03        c2t12d0s2    sliced  3199    17907200 -

pl bobvol-01    -            DISABLED -        1027200  STRIPE    3/128    RW
sd bob01-01    bobvol-01    bob01    0        342342  0/0      c1t12d0  ENA
sd bob02-01    bobvol-01    bob02    0        342342  1/0      c1t14d0  ENA
sd bob03-01    bobvol-01    bob03    0        342400  2/0      c2t12d0  ENA

Finally, the volume is made, specifying the plex just made:

# vxmake -g bobdg -U fsgen vol bobvol plex=bobvol-01
# vxprint -ht -g bobdg
DG NAME        NCONFIG      NLOG    MINORS  GROUP-ID
DM NAME        DEVICE      TYPE    PRIVLEN  PUBLEN  STATE
RV NAME        RLINK_CNT    KSTATE  STATE    PRIMARY  DATAVOLS  SRL
RL NAME        RVG          KSTATE  STATE    REM_HOST REM_DG    REM_RLNK
V  NAME        RVG          KSTATE  STATE    LENGTH  READPOL  PREFPLEX UTYPE
PL NAME        VOLUME      KSTATE  STATE    LENGTH  LAYOUT    NCOL/WID MODE
SD NAME        PLEX        DISK    DISKOFFS LENGTH  [COL/]OFF DEVICE  MODE
SV NAME        PLEX        VOLNAME  NVOLLAYR LENGTH  [COL/]OFF AM/NM    MODE
DC NAME        PARENTVOL    LOGVOL
SP NAME        SNAPVOL      DCO

dg bobdg        default      default  22000    1022089620.1237.Rawfusion

dm bob01        c1t12d0s2    sliced  2393    35833392 -
dm bob02        c1t14d0s2    sliced  2393    35833392 -
dm bob03        c2t12d0s2    sliced  3199    17907200 -

v  bobvol      -            DISABLED EMPTY    1026886  ROUND    -        fsgen
pl bobvol-01    bobvol      DISABLED EMPTY    1027200  STRIPE    3/128    RW
sd bob01-01    bobvol-01    bob01    0        342342  0/0      c1t12d0  ENA
sd bob02-01    bobvol-01    bob02    0        342342  1/0      c1t14d0  ENA
sd bob03-01    bobvol-01    bob03    0        342400  2/0      c2t12d0  ENA

The volume then needs to be started and the file system fsck'd:

# vxvol -g bobdg start bobvol
# fsck -F vxfs /dev/vx/rdsk/bobdg/bobvol

file system is clean - log replay is not required

Once mounted, the file system is checked to ensure the data is still present.

# mount -F vxfs /dev/vx/dsk/bobdg/bobvol /test1
# ls -l /test1
total 32514
drwxr-xr-x  3 root    other        96 May 22 10:38 VRTS
drwxr-xr-x  3 root    other        96 May 22 10:38 VRTSlic
drwxr-xr-x  11 root    other      1024 May 22 10:39 VRTSsamba
-rw-r--r--  1 root    other    16645973 May 22 10:39 VRTSsamba.tar.Z
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvmsa
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvras
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvxfs
drwxr-xr-x  5 root    other        96 May 22 10:39 VRTSvxvm
drwxr-xr-x  2 root    root          96 May 22 10:37 lost+found