Why is init process showing a lot of disk I/O activity after the boot sequence has been completed?

Issue

atop output shows the following:

NPROCS     SYSCPU      USRCPU      VSIZE      RSIZE      RDDSK      WRDSK     RNET     SNET      DSK     CMD       1/30
     1      0.74s       0.02s     10372K       804K     559.6M      6304K        ?        ?      61%     init
  2080     97.14s       7m23s       1.6T      14.7G     167.7M         4K        ?        ?      18%     oracle
     1      0.47s       0.43s     19936K      5136K         0K     96472K        ?        ?      10%     CVMVolDgAgent
     1      0.16s       0.09s     102.5M     28740K         0K     34320K        ?        ?       4%     vxdclid
     1      4.63s       0.00s         0K         0K     28782K         0K        ?        ?       3%     vxfs_thread