1. /dev/sdc1 is not PV-physical volume. It is just a disk.

[root@rbwqas1 ~]# pvdisplay /dev/sdc1

  Failed to find physical volume "/dev/sdc1".

/dev/sda2 is a physical volume. 

  [root@rbwqas1 ~]# pvdisplay /dev/sda2

  --- Physical volume ---

  PV Name               /dev/sda2

  VG Name               vg_rbwqas1

  PV Size               1.50 TiB / not usable 3.00 MiB

  Allocatable           yes (but full)

  PE Size               4.00 MiB

  Total PE              393090

  Free PE               0

  Allocated PE          393090

  PV UUID               zQJkjj-fq1i-vVBW-lxpK-n0Lo-WMtX-Ahgarr

2. 

[root@rbwqas1 ~]# df -hPT |grep workdir

/dev/sdc1                       ext4   296G   46G  235G  17% /workdir

3. add disk 

3.1 umount /workdir

fuser -m -v /workdir

[root@rbwqas1 /]# fuser -m -v -k -i /workdir

                     USER        PID ACCESS COMMAND

/workdir:            qasadm    12409 ..c.. csh

                     oraqas    15093 ..c.. csh

                     qasadm    15982 ..c.. csh

Kill process 12409 ? (y/N) y

Kill process 15093 ? (y/N) y

Kill process 15982 ? (y/N) y

[root@rbwqas1 /]#

[root@rbwqas1 /]# 

3.2 Create PV

[root@rbwqas1 /]# vgs

VG         #PV #LV #SN Attr   VSize VFree

vg_rbwqas1   3  43   0 wz--n- 3.09t 30.05g

[root@rbwqas1 /]# pvcreate /dev/sdc1

Physical volume "/dev/sdc1" successfully created

3.3 Add the PV into Volume Group(extend VG)

[root@rbwqas1 /]# vgextend vg_rbwqas1 /dev/sdc1

Volume group "vg_rbwqas1" successfully extended

[root@rbwqas1 /]# vgs

VG         #PV #LV #SN Attr   VSize VFree

vg_rbwqas1   4  43   0 wz--n- 3.38t 330.05g

3.4 Extend LV - Logical Volume

[root@rbwqas1 /]# lvextend -L +300G /dev/mapper/vg_rbwqas1-LogVol17

Size of logical volume vg_rbwqas1/LogVol17 changed from 1.30 TiB (340480 extents) to 1.59 TiB (417280 extents).

Logical volume LogVol17 successfully resized.

3.5 Resize2fs LV 

resize2fs /dev/mapper/vg_rbwqas1-LogVol17