fix re-open failure issue when using gluster ioengine

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index c58e81769d3585c09a808c057ed6a361ab034f3f..c61948bb52814a2a6bac248c5db0063406225a48 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -612,6 +612,17 @@ options.
 Using Glusterfs libgfapi async interface to direct access to Glusterfs volumes without
 having to go through FUSE. This ioengine defines engine specific
 options.
+.TP
+.B libhdfs
+Read and write through Hadoop (HDFS).  The \fBfilename\fR option is used to
+specify host,port of the hdfs name-node to connect. This engine interprets
+offsets a little differently. In HDFS, files once created cannot be modified.
+So random writes are not possible. To imitate this, libhdfs engine expects
+bunch of small files to be created over HDFS, and engine will randomly pick a
+file out of those files based on the offset generated by fio backend. (see the
+example job file to create such files, use rw=write option). Please note, you
+might want to set necessary environment variables to work with hdfs/libhdfs
+properly.
 .RE
 .P
 .RE
@@ -657,10 +668,11 @@ Offset in the file to start I/O. Data before the offset will not be touched.
 .TP
 .BI offset_increment \fR=\fPint
 If this is provided, then the real offset becomes the
-offset + offset_increment * thread_number, where the thread number is a counter
-that starts at 0 and is incremented for each job. This option is useful if
-there are several jobs which are intended to operate on a file in parallel in
-disjoint segments, with even spacing between the starting points.
+offset + offset_increment * thread_number, where the thread number is a
+counter that starts at 0 and is incremented for each sub-job (i.e. when
+numjobs option is specified). This option is useful if there are several jobs
+which are intended to operate on a file in parallel disjoint segments, with
+even spacing between the starting points.
 .TP
 .BI number_ios \fR=\fPint
 Fio will normally perform IOs until it has exhausted the size of the region
@@ -1191,17 +1203,21 @@ If given, write a bandwidth log of the jobs in this job file. Can be used to
 store data of the bandwidth of the jobs in their lifetime. The included
 fio_generate_plots script uses gnuplot to turn these text files into nice
 graphs. See \fBwrite_lat_log\fR for behaviour of given filename. For this
-option, the postfix is _bw.log.
+option, the postfix is _bw.x.log, where x is the index of the job (1..N,
+where N is the number of jobs)
 .TP
 .BI write_lat_log \fR=\fPstr
 Same as \fBwrite_bw_log\fR, but writes I/O completion latencies.  If no
-filename is given with this option, the default filename of "jobname_type.log"
-is used. Even if the filename is given, fio will still append the type of log.
+filename is given with this option, the default filename of
+"jobname_type.x.log" is used, where x is the index of the job (1..N, where
+N is the number of jobs). Even if the filename is given, fio will still
+append the type of log.
 .TP
 .BI write_iops_log \fR=\fPstr
 Same as \fBwrite_bw_log\fR, but writes IOPS. If no filename is given with this
-option, the default filename of "jobname_type.log" is used. Even if the
-filename is given, fio will still append the type of log.
+option, the default filename of "jobname_type.x.log" is used, where x is the
+index of the job (1..N, where N is the number of jobs). Even if the filename
+is given, fio will still append the type of log.
 .TP
 .BI log_avg_msec \fR=\fPint
 By default, fio will log an entry in the iops, latency, or bw log for every