Documentation update

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 0b438714c56cba93b9f319178231b258bb2ee47e..99cbaea37eb760dca27875eab9bcb8bd9def2292 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -170,7 +170,7 @@ Some parameters take an option of a given type, such as an integer or
 a string. The following types are used:
 
 str    String. This is a sequence of alpha characters.
-int    Integer. A whole number value, may be negative.
+int    Integer. A whole number value, can be negative.
 siint  SI integer. A whole number value, which may contain a postfix
        describing the base of the number. Accepted postfixes are k/m/g,
        meaning kilo, mega, and giga. So if you want to specify 4096,
@@ -249,12 +249,12 @@ fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
                If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
                IO and POSIX_FADV_RANDOM for random IO.
 
-size=siint     The total size of file io for this job. This may describe
-               the size of the single file the job uses, or it may be
-               divided between the number of files in the job. If the
-               file already exists, the file size will be adjusted to this
-               size if larger than the current file size. If this parameter
-               is not given and the file exists, the file size will be used.
+size=siint     The total size of file io for this job. Fio will run until
+               this many bytes has been transferred, unless runtime is
+               limited by other options (such as 'runtime', for instance).
+               Unless specific nr_files and filesize options are given,
+               fio will divide this size between the available files
+               specified by the job.
 
 filesize=siint Individual file sizes. May be a range, in which case fio
                will select sizes for files at random within the given range
@@ -419,7 +419,9 @@ norandommap Normally fio will cover every block of the file when doing
                new random offset without looking at past io history. This
                means that some blocks may not be read or written, and that
                some blocks may be read/written more than once. This option
-               is mutually exclusive with verify= for that reason.
+               is mutually exclusive with verify= for that reason, since
+               fio doesn't track potential block rewrites which may alter
+               the calculated checksum for that block.
 
 nice=int       Run the job with the given nice value. See man nice(2).
 
@@ -465,7 +467,8 @@ ratecycle=int       Average bandwidth for 'rate' and 'ratemin' over this number
 
 cpumask=int    Set the CPU affinity of this job. The parameter given is a
                bitmask of allowed CPU's the job may run on. See man
-               sched_setaffinity(2).
+               sched_setaffinity(2). This may not work on all supported
+               operating systems or kernel versions.
 
 startdelay=int Start this job the specified number of seconds after fio
                has started. Only useful if the job file contains several
@@ -618,7 +621,12 @@ write_iolog=str    Write the issued io patterns to the specified file. See
 
 read_iolog=str Open an iolog with the specified file name and replay the
                io patterns it contains. This can be used to store a
-               workload and replay it sometime later.
+               workload and replay it sometime later. The iolog given
+               may also be a blktrace binary file, which allows fio
+               to replay a workload captured by blktrace. See blktrace
+               for how to capture such logging data. For blktrace replay,
+               the file needs to be turned into a blkparse binary data
+               file first (blktrace <device> -d file_for_fio.bin).
 
 write_bw_log   If given, write a bandwidth log of the jobs in this job
                file. Can be used to store data of the bandwidth of the