Original wbtest is * Copyright (C) 2003-2004 EMC Corporation * * wbtest.c - a testing utility for the write barrier file system  *            functionality. * * Written by Brett Russ <russb@emc.com>rewritten to match my needs Copyright 2004 Lars Ellenberg <l.g.e@web.de>----wbtest.c READMEIntentional Usage:You should setup a pair of DRBD, mount it on one node, and run wbteston some path on that device. Then you can trigger more or less gracefullfailovers, and run wbtest on the other node.Compile:Easy!:  gcc -o wbtest wbtest.cSummary:The program starts and first scans the data dir for files matching theexpected naming convention. All unfinished files (ending in '+') willthen just be unlinked, all other files will be verified to match theirexpected size and content.This data dir should be empty on first run.  Finding none, wbtest willbegin to create processes whose job is to create new data files.  Eachprocess writes a number of files of size in range <min> to <max>(default 4B -- 100KB) and then exits.  A max of <concurrent> procs arelaunched at once.  A pass is defined as the cycle a process makes from<min> to <max> or <max> to <min>; odd PIDs ascend, even PIDs descend.A <passes> value of 0 runs to infinity.  After <recycle> passes, wbteststarts to verify and remove single passes again, to avoid to fill up thefile system completely.The point is to cut off power to the running machine at a random pointduring the testing.  To do this, either set <passes> to 0 or ensurethat you set it high enough such that I/O is running when the power isshut off.On failover or reboot, the test data files are verified.The file naming convention controlls the verification of the test data.These files are named <pid>-<size>-<hexdigits>, and are expected to beof size <size>, and to be filled with the four byte pattern <hexdigits>.A file ending in an additional '+' was not yet completely written, so itis not expected to verify correctly. It will just be removed in theverification step.If errors are found, testing stops and if a log file was provided thefile in error is logged.  All test data files that verify successfullyare removed.  Any test data files with errors are preserved forinspection.I think that's about it...here's the usage text:Usage: ./wbtest [-hvV] [-m <min>] [-M <max>] [-p <passes>]		[-r <recycle>] [-c <concurrent>] [-l <vLog>] -d <datadir>./wbtest - Version 1.1-lge Options:  -h prints this usage text  -v SKIP verification step of existing files (if any)  -V forces exit after verification step of existing files  min         minimum IO size to use (bytes)  max         maximum IO size to use (bytes)  passes      # of passes to run (0 for INF)  recycle     # of passes after which recycling of disk space starts  concurrent  # of processes to run at once  vLog        log (append) all file verify failures here.              otherwise /tmp/wbtest-vLog-<timestamp>-<pid> will be used  datadir     required; writable directory on DRBD to store 'test data' files