
	VDT	Readme

This is the `README' file for VDT ( The Visual Disk Test by <botao.org> )

	What is VDT ?

Vdt is a disk/file/device i/o test program, with visual feedback/follow-up.

	Tarball

Vdt is distributed in a tar-gzipped archive, and to open it, simply :

$ gzip -d vdt-<version>-src.tar.gz
$ tar xvf vdt-<version>-src.tar

	Source-code directory

After the steps above, go to the source-code directory, called `vdt<number>' (eg.: 'vdt5') :

$ cd vdt<number>

	Installation

Building could hardly be simpler; just unpack it, and in the source directory :

$ ./configure
$ make
$ make install

- and you're done, gnu-style (2).

	Validation

Optionally, you can

$ make test

right after `make' (or at any later time),
just to validate some key features and functions.

	Concepts

VDT operates on sector-groups called B.o.S. (Bunch-of-Sectors),
so that all (or most) I/O operations are done in chunks of this size.

-- If the file size is not a multiple of the 'lumpsize', then the last of
the sector-groups will have a smaller size.

The 'seek' times refer to the action of 'seek to read from the first
(or only) input file'.

The 'peek' times refer to the action of 'seek to read from the second
input file' in the 'comparison' test.

The 'riff' times refer to the action of 'actually reading from the second
input file' in the 'comparison' test.

The 'jump' times may refer to:
- the action of 'seek to write on the output file' in the 'poke' or 'writ' tests, or
- the action of 'seek to write on the second (output) file' in the 'copy' test, or
- the action of 'seek to write back on the (input/output) file' in the 'cool' test.

The '-t #' option is a time barrier.

The '--wrap' options extends test duration until timeout by restarting upon completion.

	Reports

VDT's log file shows a report of sizes, regions, speeds, performances,
for read, write, seek, and any other used/tested features.

VDT reports the best, worst, and average results as follows:

- performance results are prefixed 'max', 'min, and 'avg' respectively ;

- time results are marked inversely, so that 'max' times are longer times
and consequently 'worst' times in the spirit of the test, and so on for
'best' times, marked as 'min'.

The performance records above are based on the (possibly atomic) I/O of a sector-group ;

VDT also emits a 'net' performance, based on the total bytes transferred and
the (real) elapsed time of the whole test loop.

	Development

Vdt is an ongoing project,
so the 'TODO' file has quite a few tasks, plans, ideas
still to be implemented in due time.

	Warnings

Using VDT with `root' privileges (1) to access special device files
possibly can and most certainly will cause problems
if you do not know what you are doing.

Although all of the 'read'-type tests are harmless, the 'write'-type ones
are sure to disrupt any pre-existing data involved, even the superblock(s)
if it is applied to a logical volume or partition containing a filesystem.

	Feedback

Bug reports should be directed to the `support' facility at SourceForge;
However, any comment, improvement/enhencement suggestions, problem report,
or general feedback can be sent by email and is very welcome.

In the case of bug/problem report, please include specific details about
the operating system, compiler, processor architecture, and version number.

	Notes

(1) Using ANY software with `root' privileges requires appropriate knowledge.

(2) The Vdt 'build' is NOT (yet) converted to gnu-autotools.

- Vdt is tested OK with file sizes not smaller than 256KiB.

____________________________________________________________
September 2010,
Alexandre Botao.
