All raw data is recorded in a single compressed file with the extension
raw.gz if the perl compression library has been installed. If that
library is not there it will be written to a non-compressed file with the
extension raw. The only exception to this rule is the process
raw file which can be useful on systems with a large number of processes
(see the description of --tworaw) and which has the extension rawp.
There are actually 2 main types of plot data - summary and detail.
Summary plot data, for those subsystems selected with lower case letters,
is always stored in a single file, one line per time period,
with the extension tab. The primary reason for this is that the data for
each subsystem is of a fixed length and there is really no benefit in
separating it into multiple files.
Detail plot data, which is typically for devices for which there can be multiple
instances such as CPUs, is recorded in one file per detail type with an extension
that reflects the type of data stored in that file.
Each line contains instance data of a fixed number of
fields for that particular device. Although TCP do not have instance data,
it does have a detail component and is also written to its own detail file.
Process and Slab data are also treated like detail data because they too require
multiple lines per monitoring period.
Exception data is written to a file in the same format as detail data with an
X appended to its name. Since exception data is not of a known format
across the entire device as is detail data, it cannot be written as a single
line, but rather is written as one line per device. Each line is prefaced with
a date/time stamp and the number of the device (0 based).
Periodically collectl logs various types of messages to its own message log to avoid
situations in which an unexpected situation or a collectl bug might causes the
flooding of /var/log/mesasages. However, the more serious messages are written to
both as described here.