Can pstat_getdisk() and iostat be of some help to you ?

#include <sys/pstat/disk_pstat_body.h>
struct __pst_diskinfo {
_T_LONG_T psd_dkxfer; /* cumulative number of transfers;
* includes requests with high
* (read/write) and low (ioctl)
priorities
.... */
}

The number of bytes transferred to disk can be found out by using iostat.
column significance
device Device name
bps Kilobytes transferred per second

---
Regards
Surinder Kumar
x 3194

A smooth sea never made a skillful mariner