There is many useful DTrace tools for sysadmins.

One of my favorite is iotop, maybe one of the most useful DTrace script.

This simple handy tool is a top-like measuring filesystem access (disk events that have made it past system caches to be more precise).

Here's an example of the output on a Solaris box running multiple zones :

2007 Jul  9 11:02:59,  load: 4.50,  disk_r:   1297 KB,  disk_w:   1241 KB

 ZONE    PID   PPID CMD              DEVICE  MAJ MIN D            BYTES
    1    916      1 ns-slapd         sd0      32   5 R           131072
    2   1056      1 nscd             sd0      32   5 R           262144
    1    518      1 snmpd            sd0      32   5 R           279552
    1    549      1 nscd             sd0      32   5 R           327680
    2   1385      1 ns-slapd         sd0      32   5 R           327680
    0      0      0 sched            sd0      32   5 W          1270784

Check also the others DTrace scripts like ExecSnoop on Brendan Gregg's site and the Opensolaris DTrace community. And of course, send us your comments with your favorites DTrace tools !