This version documents the switch `--write-journal`.

```
       --write-journal
              Specify  journal  device  for  the RAID-4/5/6 array. The journal device should be a SSD
              with reasonable lifetime.
```

Announcement [2]:

> Subject: ANNOUNCE: mdadm 4.0 - A tool for managing md Soft RAID under Linux
>
> I am pleased to announce the availability of
>    mdadm version 4.0
>
> It is available at the usual places:
>    https://www.kernel.org/pub/linux/utils/raid/mdadm/
> and via git at
>    git://git.kernel.org/pub/scm/utils/mdadm/mdadm.git
>    https://git.kernel.org/cgit/utils/mdadm/
>
> The update in major version number primarily indicates this is a
> release by it's new maintainer. In addition it contains a large number
> of fixes in particular for IMSM RAID and clustered RAID support.  In
> addition this release includes support for IMSM 4k sector drives,
> failfast and better documentation for journaled RAID.
>
> This is my first release of mdadm. Please thank Neil Brown for his
> previous work as maintainer and blame me for all the bugs I caused
> since taking over.
>
> Jes Sorensen, 2017-01-09

[1] http://www.linuxfromscratch.org/blfs/view/8.0/postlfs/mdadm.html
[2] https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/tree/ANNOUNCE-4.0

Building in parallel fails, so try to avoid it.

```
$ make -j62 PREFIX=/usr EPREFIX=/usr BINDIR=/usr/bin SBINDIR=/usr/sbin LIBEXECDIR=/usr/libexec SYSCONFDIR=/etc SHAREDSTATEDIR=/var LOCALSTATEDIR=/var LIBDIR=/usr/lib INCLUDEDIR=/usr/include DATAROOTDIR=/usr/share DATADIR=/usr/share INFODIR=/usr/share/info LOCALEDIR=/usr/share/locale MANDIR=/usr/share/man DOCDIR=/usr/share/doc/mdadm V=1 everything
[…]
cc -o mdadm.Os -Wall -Werror -Wstrict-prototypes -Wextra -Wno-unused-parameter -ggdb -DSendmail=\""/usr/sbin/sendmail -t"\" -DCONFFILE=\"/etc/mdadm.conf\" -DCONFFILE2=\"/etc/mdadm/mdadm.conf\" -DMAP_DIR=\"/run/mdadm\" -DMAP_FILE=\"map\" -DMDMON_DIR=\"/run/mdadm\" -DFAILED_SLOTS_DIR=\"/run/mdadm/failed-slots\" -DNO_COROSYNC -DNO_DLM -DUSE_PTHREADS -DBINDIR=\"/usr/bin\"  -DHAVE_STDINT_H -Os mdadm.c config.c policy.c mdstat.c ReadMe.c util.c maps.c lib.c Manage.c Assemble.c Build.c Create.c Detail.c Examine.c Grow.c Monitor.c dlink.c Kill.c Query.c Incremental.c Dump.c mdopen.c super0.c super1.c super-ddf.c super-intel.c bitmap.c super-mbr.c super-gpt.c restripe.c sysfs.c sha1.c mapfile.c crc32.c sg_io.c msg.c xmalloc.c platform-intel.c probe_roms.c crc32c.c -ldl
cc -o mdmon.O2 -Wall -Werror -Wstrict-prototypes -Wextra -Wno-unused-parameter -ggdb -DSendmail=\""/usr/sbin/sendmail -t"\" -DCONFFILE=\"/etc/mdadm.conf\" -DCONFFILE2=\"/etc/mdadm/mdadm.conf\" -DMAP_DIR=\"/run/mdadm\" -DMAP_FILE=\"map\" -DMDMON_DIR=\"/run/mdadm\" -DFAILED_SLOTS_DIR=\"/run/mdadm/failed-slots\" -DNO_COROSYNC -DNO_DLM   -DUSE_PTHREADS -DBINDIR=\"/usr/bin\"  -pthread -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 mdmon.c monitor.c managemon.c util.c maps.c mdstat.c sysfs.c policy.c lib.c Kill.c sg_io.c dlink.c ReadMe.c super-intel.c super-mbr.c super-gpt.c super-ddf.c sha1.c crc32.c msg.c bitmap.c xmalloc.c platform-intel.c probe_roms.c -ldl
sed -e 's/{DEFAULT_METADATA}/1.2/g' \
-e 's,{MAP_PATH},/run/mdadm/map,g'  mdadm.8.in > mdadm.8
man -l md.4 > md.man
man -l mdadm.conf.5 > mdadm.conf.man
man -l mdmon.8 > mdmon.man
man -l raid6check.8 > raid6check.man
man -l mdadm.8 > mdadm.man
rm -f mdadm.o config.o policy.o mdstat.o  ReadMe.o util.o maps.o lib.o Manage.o Assemble.o Build.o Create.o Detail.o Examine.o Grow.o Monitor.o dlink.o Kill.o Query.o Incremental.o Dump.o mdopen.o super0.o super1.o super-ddf.o super-intel.o bitmap.o super-mbr.o super-gpt.o restripe.o sysfs.o sha1.o mapfile.o crc32.o sg_io.o msg.o xmalloc.o platform-intel.o probe_roms.o crc32c.o
cc  -DBINDIR=\"/usr/bin\" -Wall -Werror -Wstrict-prototypes -Wextra -Wno-unused-parameter -ggdb -DSendmail=\""/usr/sbin/sendmail -t"\" -DCONFFILE=\"/etc/mdadm.conf\" -DCONFFILE2=\"/etc/mdadm/mdadm.conf\" -DMAP_DIR=\"/run/mdadm\" -DMAP_FILE=\"map\" -DMDMON_DIR=\"/run/mdadm\" -DFAILED_SLOTS_DIR=\"/run/mdadm/failed-slots\" -DNO_COROSYNC -DNO_DLM   -DUSE_PTHREADS -DMDASSEMBLE -DMDASSEMBLE_AUTO -static -DHAVE_STDINT_H -o mdassemble.static mdassemble.c Assemble.c Manage.c config.c policy.c dlink.c util.c maps.c lib.c xmalloc.c super0.c super1.c super-ddf.c super-intel.c sha1.c crc32.c sg_io.c mdstat.c platform-intel.c probe_roms.c sysfs.c super-mbr.c super-gpt.c mapfile.c mdopen.c pwgr.c
cc -ggdb  -o raid6check raid6check.o restripe.o sysfs.o maps.o lib.o xmalloc.o dlink.o
cc: error: restripe.o: No such file or directory
cc: error: sysfs.o: No such file or directory
cc: error: maps.o: No such file or directory
cc: error: lib.o: No such file or directory
cc: error: xmalloc.o: No such file or directory
cc: error: dlink.o: No such file or directory
Makefile:217: recipe for target 'raid6check' failed
make: *** [raid6check] Error 1
make: *** Waiting for unfinished jobs....
/usr/bin/ld: cannot find xmalloc.o: No such file or directory
collect2: error: ld returned 1 exit status
Makefile:214: recipe for target 'test_stripe' failed
make: *** [test_stripe] Error 1
make[1]: Leaving directory '/dev/shm/bee-joey/mdadm/mdadm-4.0-0/source'
mv mdassemble.static mdassemble.auto
```