Veritas Snapshots !!!

A Veritas Snapshot is used to create the snap of a particular volume.A snap represents the data exists in a volume at a given point of time.Thus using snapshot we can even rollback the current situation of a DG and we can also create a copy of the filesystem at that particular point of time.

# bash
bash-3.2#
bash-3.2#
bash-3.2# df -kh
Filesystem             size   used  avail capacity  Mounted on
rpool/ROOT/s10s_u11wos_24a
                        15G   5.3G   5.8G    48%    /
/devices                 0K     0K     0K     0%    /devices
ctfs                     0K     0K     0K     0%    /system/contract
proc                     0K     0K     0K     0%    /proc
mnttab                   0K     0K     0K     0%    /etc/mnttab
swap                   7.3G   464K   7.3G     1%    /etc/svc/volatile
objfs                    0K     0K     0K     0%    /system/object
sharefs                  0K     0K     0K     0%    /etc/dfs/sharetab
swap                   7.3G     0K   7.3G     0%    /dev/vx/dmp
swap                   7.3G     0K   7.3G     0%    /dev/vx/rdmp
/platform/SUNW,SPARC-Enterprise-T5120/lib/libc_psr/libc_psr_hwcap2.so.1
                        11G   5.3G   5.8G    48%    /platform/sun4v/lib/libc_psr.so.1
/platform/SUNW,SPARC-Enterprise-T5120/lib/sparcv9/libc_psr/libc_psr_hwcap2.so.1
                        11G   5.3G   5.8G    48%    /platform/sun4v/lib/sparcv9/libc_psr.so.1
fd                       0K     0K     0K     0%    /dev/fd
swap                   7.3G    32K   7.3G     1%    /tmp
swap                   7.3G    40K   7.3G     1%    /var/run
rpool/export            15G    32K   5.8G     1%    /export
rpool/export/home       15G    31K   5.8G     1%    /export/home
rpool                   15G   106K   5.8G     1%    /rpool
/dev/odm                 0K     0K     0K     0%    /dev/odm
/dev/vx/dsk/datadg/vol1
                        20G   2.4G    16G    13%    /mysap
bash-3.2#
bash-3.2# cd /mysap
bash-3.2#
bash-3.2# ls -lrth
total 4194320
drwxr-xr-x   7 root     root          96 Sep  4  2013 ASCS03
drwxr-xr-x   2 root     root          96 Jul 19 05:52 lost+found
-rw-r--r--   1 root     root        2.0G Jul 21 10:31 pacct
bash-3.2#
bash-3.2# vxprint -ht
Disk group: datadg

dg datadg       default      default  10000    1405729182.10.test1

dm disk1        emc_clariion0_192 auto 65535   142524320 -
dm disk2        emc_clariion0_194 auto 65535   142524320 -

v  vol1         -            ENABLED  ACTIVE   41943040 SELECT    -        fsgen
pl vol1-01      vol1         ENABLED  ACTIVE   41943040 CONCAT    -        RW
sd disk2-01     vol1-01      disk2    0        41943040 0         emc_clariion0_194 ENA
bash-3.2#

For the snapshot , first of all we need a SNAP of volume then only we can start a SNAPSHOT.
Now let us start the snap.....

bash-3.2# vxassist -g datadg snapstart vol1
bash-3.2#
bash-3.2#
bash-3.2# vxprint -ht
Disk group: datadg

dg datadg       default      default  10000    1405729182.10.test1

dm disk1        emc_clariion0_192 auto 65535   142524320 -
dm disk2        emc_clariion0_194 auto 65535   142524320 -

v  vol1         -            ENABLED  ACTIVE   41943040 SELECT    -        fsgen
pl vol1-01      vol1         ENABLED  ACTIVE   41943040 CONCAT    -        RW
sd disk2-01     vol1-01      disk2    0        41943040 0         emc_clariion0_194 ENA
pl vol1-02      vol1         ENABLED  SNAPDONE 41943040 CONCAT    -        WO
sd disk1-01     vol1-02      disk1    0        41943040 0         emc_clariion0_192 ENA
bash-3.2#

In above output we can observe that a SNAP is DONE, now we are ready to start a snapshot from the SNAP which we took already.

bash-3.2#
bash-3.2#
bash-3.2# vxassist -g datadg snapshot vol1 snap-vol1
bash-3.2#
bash-3.2#
bash-3.2# vxprint -ht
Disk group: datadg

dg datadg       default      default  10000    1405729182.10.test1

dm disk1        emc_clariion0_192 auto 65535   142524320 -
dm disk2        emc_clariion0_194 auto 65535   142524320 -

v  snap-vol1    -            ENABLED  ACTIVE   41943040 ROUND     -        fsgen
pl vol1-02      snap-vol1    ENABLED  ACTIVE   41943040 CONCAT    -        RW
sd disk1-01     vol1-02      disk1    0        41943040 0         emc_clariion0_192 ENA

v  vol1         -            ENABLED  ACTIVE   41943040 SELECT    -        fsgen
pl vol1-01      vol1         ENABLED  ACTIVE   41943040 CONCAT    -        RW
sd disk2-01     vol1-01      disk2    0        41943040 0         emc_clariion0_194 ENA
bash-3.2#

By this we completed the snapshot of the volume, now this particular snapshot acts as an individual volume.We can even mount this volume as a Filesystem.

bash-3.2#
bash-3.2# mount -F vxfs /dev/vx/dsk/datadg/snap-vol1 /mnt
bash-3.2#
bash-3.2#
bash-3.2# df -kh
Filesystem             size   used  avail capacity  Mounted on
rpool/ROOT/s10s_u11wos_24a
                        15G   5.3G   5.8G    48%    /
/devices                 0K     0K     0K     0%    /devices
ctfs                     0K     0K     0K     0%    /system/contract
proc                     0K     0K     0K     0%    /proc
mnttab                   0K     0K     0K     0%    /etc/mnttab
swap                   7.3G   464K   7.3G     1%    /etc/svc/volatile
objfs                    0K     0K     0K     0%    /system/object
sharefs                  0K     0K     0K     0%    /etc/dfs/sharetab
swap                   7.3G     0K   7.3G     0%    /dev/vx/dmp
swap                   7.3G     0K   7.3G     0%    /dev/vx/rdmp
/platform/SUNW,SPARC-Enterprise-T5120/lib/libc_psr/libc_psr_hwcap2.so.1
                        11G   5.3G   5.8G    48%    /platform/sun4v/lib/libc_psr.so.1
/platform/SUNW,SPARC-Enterprise-T5120/lib/sparcv9/libc_psr/libc_psr_hwcap2.so.1
                        11G   5.3G   5.8G    48%    /platform/sun4v/lib/sparcv9/libc_psr.so.1
fd                       0K     0K     0K     0%    /dev/fd
swap                   7.3G    32K   7.3G     1%    /tmp
swap                   7.3G    40K   7.3G     1%    /var/run
rpool/export            15G    32K   5.8G     1%    /export
rpool/export/home       15G    31K   5.8G     1%    /export/home
rpool                   15G   106K   5.8G     1%    /rpool
/dev/odm                 0K     0K     0K     0%    /dev/odm
/dev/vx/dsk/datadg/vol1
                        20G   2.4G    16G    13%    /mysap
/dev/vx/dsk/datadg/snap-vol1
                        20G   2.4G    16G    13%    /mnt
bash-3.2#

Some more useful commands related to vxsnaps:

To take snapshot of all volumes of a DG....

bash-3.2# vxassist -g datadg -o allvols snapshot

To clear a snap.... (Remember it is clearing a snap, but not the snapshot)

bash-3.2# vxassist -g datadg snapclear snap-vol1