I have configured multipath and in lvm.conf I have added

filter = [ "^/dev/mpath/*/", "r/.*/" ]
preferred_names = [ "^/dev/mpath/", "^/dev/mapper/mpath", "^/dev/[hs]d" ]

line for filter, after going through some posts I found that pvscan need to be given before rebooting the server. Can anyone tell me the desired output I should get for pvscan and is it necessary to give it, if so why.

pvscan will simply ouput the physical volumes (PVs) it finds:
Example:
PV /dev/sdb1 VG vg_Database lvm2 [1.64 TiB / 0 free]
PV /dev/mapper/mpathd VG vg_pgpdb lvm2 [1.47 TiB / 0 free]
PV /dev/mapper/mpathe VG vg_pgparch lvm2 [249.97 GiB / 0 free]
PV /dev/sda2 VG VolGroup00 lvm2 [557.88 GiB / 319.79 GiB free]
Total: 4 [3.89 TiB] / in use: 4 [3.89 TiB] / in no VG: 0 [0 ]

However, your filter is:
a) Incorrect because you would need to prepend with a/ to tell it to accept.
b) Unnecessary when using multipath devices. You should focus instead on the multipath.conf. For our systems with mutlipath we use the default filter:
filter = [ "a/.*/" ]

I have now configured as below

filter = [ "r/disk/", "r/sd.*/", "a/.*/" ]
preferred_names = [ "^/dev/mpath/", "^/dev/mapper/mpath", "^/dev/[hs]d" ]