Devices md(7D)
NAME
md - user configurable pseudo device driver
DESCRIPTION
md is a user configurable pseudo device driver that provides
disk concatenation, striping, mirroring, RAID5 metadevices,
trans metadevices, and hot spare utilities. Trans devices
are no longer supported and have been replaced by UFS log-
ging. See mountufs(1M).
The block devices access the disk using the system's normal
buffering mechanism and are read and written without regard
to physical disk records. There is also a ``raw'' device
which provides for direct transmission between the disk and
the user's read or write buffer. A single read or write call
usually results in one I/O operation; raw I/O is therefore
considerably more efficient when many bytes are transmitted.
The names of the block devices are found in /dev/md/dsk; the
names of the raw devices are found in /dev/md/rdsk. Metadev-
ices have the appearance of whole disks; there are no slices
(partitions).
I/O requests (such as lseek(2)) to the metadevices must have
an offset that is a multiple of 512 bytes (DEVBSIZE), or
the driver returns an EINVAL error. If the transfer length
is not a multiple of 512 bytes, the tranfer count is rounded
up by the driver.
The md pseudo device drivers support all disk devices on all
Solaris 2.4 or later Solaris systems.
IOCTLS
This section provides a list of the ioctls supported by the
metadisk driver.
The following ioctls are valid when issued to the raw meta-
device, such as /dev/md/rdsk/d0. See dkio(7I) for additional
information.
DKIOCGEOM This ioctl is used to get the disk geometry.
The metadisk driver fills in the dkgnhead,
dkgnsect, dkgrpm, dkgwritereinstruct and
dkgreadreinstruct from the first component
of the metadevice (at metainit time). dkgncyl
is calculated using the size of the metadevice
(reported by metastat) divided by (dkgnhead *
dkgnsect). The total size is always a multi-
ple of (dkgnhead * dkgnsect). If the first
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Devices md(7D)
component of a metadevice does not start on
cylinder number 0, then the dkgncyl is
increased by one cylinder; because DKIOCGVTOC
reports the metadevice as starting on cylinder
1. The side effect here is that it looks like
cylinder 0 is not being used, but all the
arithmetic works out correctly. If the meta-
device is not set up, then ENXIO is returned.
DKIOCINFO When issued to the administrative device or
metadevice, this ioctl sets dkiunit to the
unit number of the metadevice, dkictype to a
value of DKCMD, and dkipartition to 0,
because there are no slices.
DKIOCGVTOC This ioctl returns the current vtoc. If one
has not been written, then a default vtoc is
returned. vnparts is always 1.
vpart[0].pstart is 0 if the first component
of the metadevice starts on cylinder 0. Other-
wise, the pstart field is the starting sector
of cylinder 1. vpart[0].psize is the same as
the total size reported by metastat.
DKIOCSVTOC This ioctl stores the vtoc in the metadevice
state database so it is persistent across
reboots.
DIAGNOSTICS
Notice Log Messages
The informative log messages include:
md: dnum: Hotspared device dev with dev
The first device name listed has been hot spare replaced
with the second device name listed.
md: dnum: Hotspared device dev(num,num) with dev(num,num)
The first device number listed has been hot spare replaced
with the second device number listed.
md: Could not load misc /dev
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Devices md(7D)
The named misc module is not loadable. It is possibly miss-
ing, or something else has been copied over it.
md: dnum: no mem for property dev
Memory could not be allocated in the propop entry point.
md: db: Parsing error on 'dev'
Set command in /kernel/drv/md.conf for the mddb.bootlist
is not in the correct format. metadb -p can be run
to put the correct set commands into the /kernel/drv/md.conf
file.
md: dnum: dev(num,num) needs maintenance
md: dnum: dev needs maintenance
An I/O or open error has occurred on a device within a mir-
ror causing a component in the mirror to change to the
Maintenance state.
md: dnum: dev(num,num) last erred md: dnum: dev last erred
An I/O or open error has occurred on a device within a mir-
ror and the data is not replicated elsewhere in the mirror.
This is causing the component in the mirror to change to the
Last Erred state.
Warning Log Messages
The warning log messages include:
md: State database is stale
This error message comes when there are not enough usable
replicas for the state database to be able to update records
in the database. All accesses to the metadevice driver will
fail. To fix this problem, more replicas need to be added or
inaccessible replicas need to be deleted.
md: dnum: read error on devmd: dnum: write error on dev
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Devices md(7D)
A read or write error has occurred on the specified submir-
ror, at the specified device name. This happens if any read
or write errors occur on a submirror.
md: dnum: read error on dev(num,num)md: dnum: write error on dev(
num,num)
A read or write error has occurred on the specified submir-
ror, at the specified device number. This happens if any
read or write errors occur on a submirror.
md: State database commit failed
md: State database delete failed
These messages occur when there have been device errors on
components where the state database replicas reside. These
errors only occur when more than half of the replicas have
had device errors returned to them. For instance, if you
have three components with state database replicas and two
of the components report errors, then these errors may
occur. The state database commit or delete is retried
periodically. If a replica is added, then the commit or
delete will finish and the system will be operational. Oth-
erwise the system will timeout and panic.
md: dnum: Cannot load dev driver
Underlying named driver module is not loadable (for example,
sd, id, xy, or a third-party driver). This could indicate
that the driver module has been removed.
md: Open error of hotspare devmd: Open error of hotspare dev(num,num)
Named hotspare is not openable, or underlying driver is not
loadable.
Panic Log Messages
The panic log messages include:
md: dnum: Unknown close typemd: dnum: Unknown open type
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Devices md(7D)
Metadevice is being opened/closed with an unknown open type
(OTYP).
md: State database problem
Failed metadevice state database commit or delete has been
retried the default 100 times.
FILES
/dev/md/dsk/dn block device (where n is the
device number)
/dev/md/rdsk/dn raw device (where n is the
device number)
/dev/md/setname/dsk/dn block device (where setname is
the name of the diskset and n
is the device number)
/dev/md/setname/rdsk/dn raw device (where setname is
the name of the diskset and n
is the device number)
/dev/md/admin administrative device
/kernel/drv/md driver module
/kernel/drv/md.conf driver configuration file
/kernel/misc/mdstripe stripe driver misc module
/kernel/misc/mdmirror mirror driver misc module
/kernel/misc/mdhotspares hotspares driver misc module
/kernel/misc/mdtrans metatrans driver for UFS log-
ging
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Devices md(7D)
/kernel/misc/mdraid RAID5 driver misc module
SEE ALSO
mdmonitord(1M), metaclear(1M), metadb(1M), metadetach(1M),
metahs(1M), metainit(1M), metaoffline(1M), metaonline(1M),
metaparam(1M), metarecover(1M), metarename(1M),
metareplace(1M), metaroot(1M), metassist(1M), metaset(1M),
metastat(1M), metasync(1M), metattach(1M), md.cf(4),
md.tab(4), attributes(5),
Solaris Volume Manager Administration Guide
NOTES
Trans metadevices have been replaced by UFS logging. Exist-
ing trans devices are not logging--they pass data directly
through to the underlying device. See mountufs(1M) for more
information about UFS logging.
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