Expand on fill_device option since it apparently causes confusion

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index 9ca38abcdc6c69e48f39ec6c7c1b9d03a1baa3f8..a6547eefb55e5792169d78c8b0da2634142a1ded 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -226,7 +226,7 @@ are likely to be issued. Default: true.
 .BI size \fR=\fPint
 Total size of I/O for this job.  \fBfio\fR will run until this many bytes have
 been transfered, unless limited by other options (\fBruntime\fR, for instance).
-Unless \fBnr_files\fR and \fBfilesize\fR options are given, this amount will be
+Unless \fBnrfiles\fR and \fBfilesize\fR options are given, this amount will be
 divided between the available files for the job. If not set, fio will use the
 full size of the given files or devices. If the the files do not exist, size
 must be given.
@@ -235,7 +235,9 @@ must be given.
 Sets size to something really large and waits for ENOSPC (no space left on
 device) as the terminating condition. Only makes sense with sequential write.
 For a read workload, the mount point will be filled first then IO started on
-the result.
+the result. This option doesn't make sense if operating on a raw device node,
+since the size of that is already known by the file system. Additionally,
+writing beyond end-of-device will not return ENOSPC there.
 .TP
 .BI filesize \fR=\fPirange
 Individual file sizes. May be a range, in which case \fBfio\fR will select sizes
@@ -331,7 +333,13 @@ coalescing adjacents IOs into a single submission.
 Linux native asynchronous I/O.
 .TP
 .B posixaio
-glibc POSIX asynchronous I/O using \fIaio_read\fR\|(3) and \fIaio_write\fR\|(3).
+POSIX asynchronous I/O using \fIaio_read\fR\|(3) and \fIaio_write\fR\|(3).
+.TP
+.B solarisaio
+Solaris native asynchronous I/O.
+.TP
+.B windowsaio
+Windows native asynchronous I/O.
 .TP
 .B mmap
 File is memory mapped with \fImmap\fR\|(2) and data copied using
@@ -379,7 +387,13 @@ Loads an external I/O engine object file.  Append the engine filename as
 .RE
 .TP
 .BI iodepth \fR=\fPint
-Number of I/O units to keep in flight against the file.  Default: 1.
+Number of I/O units to keep in flight against the file. Note that increasing
+iodepth beyond 1 will not affect synchronous ioengines (except for small
+degress when verify_async is in use). Even async engines my impose OS
+restrictions causing the desired depth not to be achieved.  This may happen on
+Linux when using libaio and not setting \fBdirect\fR=1, since buffered IO is
+not async on that OS. Keep an eye on the IO depth distribution in the
+fio output to verify that the achieved depth is as expected. Default: 1.
 .TP
 .BI iodepth_batch \fR=\fPint
 Number of I/Os to submit at once.  Default: \fBiodepth\fR.
@@ -680,6 +694,11 @@ has to be a hex number that starts with either "0x" or "0X". Use with
 If true, exit the job on the first observed verification failure.  Default:
 false.
 .TP
+.BI verify_dump \fR=\fPbool
+If set, dump the contents of both the original data block and the data block we
+read off disk to files. This allows later analysis to inspect just what kind of
+data corruption occurred. On by default.
+.TP
 .BI verify_async \fR=\fPint
 Fio will normally verify IO inline from the submitting thread. This option
 takes an integer describing how many async offload threads to create for IO
@@ -698,13 +717,16 @@ once that job has completed. In other words, everything is written then
 everything is read back and verified. You may want to verify continually
 instead for a variety of reasons. Fio stores the meta data associated with an
 IO block in memory, so for large verify workloads, quite a bit of memory would
-be used up holding this meta data. If this option is enabled, fio will verify
-the previously written blocks before continuing to write new ones.
+be used up holding this meta data. If this option is enabled, fio will write
+only N blocks before verifying these blocks.
 .TP
 .BI verify_backlog_batch \fR=\fPint
 Control how many blocks fio will verify if verify_backlog is set. If not set,
 will default to the value of \fBverify_backlog\fR (meaning the entire queue is
-read back and verified).
+read back and verified).  If \fBverify_backlog_batch\fR is less than 
+\fBverify_backlog\fR then not all blocks will be verified,  if 
+\fBverify_backlog_batch\fR is larger than \fBverify_backlog\fR,  some blocks
+will be verified more than once.
 .TP
 .B stonewall
 Wait for preceeding jobs in the job file to exit before starting this one.
@@ -734,7 +756,9 @@ Skip the specified number of bytes when \fBzonesize\fR bytes of data have been
 read.
 .TP
 .BI write_iolog \fR=\fPstr
-Write the issued I/O patterns to the specified file.
+Write the issued I/O patterns to the specified file.  Specify a separate file
+for each job, otherwise the iologs will be interspersed and the file may be
+corrupt.
 .TP
 .BI read_iolog \fR=\fPstr
 Replay the I/O patterns contained in the specified file generated by