1 The following are demonstrations of the rfsio.d script.
5 Here we trace file read() activity that has fully missed the cache and
6 must be read from disk,
17 Read Bandwidth (bytes)
20 /boot physical 1512960
21 /extra1 physical 97153024
22 /extra1 logical 97228668
24 Total File System miss-rate: 100%
27 The miss rate of 100% means that all of the file system activity missed
28 the cache, and had to read from disk.
32 The following demonstrates file read() activity to the root filesystem
33 that mostly returned from the file system cache.
44 Read Bandwidth (bytes)
48 /extra1 physical 917504
49 /extra1 logical 4194304
51 Total File System miss-rate: 22%
54 The total miss-rate was 22%, which is based on the bytes transferred that
60 Now for an unusual demonstration,
70 Read Bandwidth (bytes)
73 /extra1 logical 64846450
74 /extra1 physical 66151424
76 Total File System miss-rate: 102%
79 Here the miss-rate is 102%, which indicates that more data was read from
80 disk than was requested; this can occur due to UFS read-ahead, which
81 assists the performance of sequential disk activity at the small risk of
82 reading too much data.