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.
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 (DEV_BSIZE),
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(7) for additional
information.
DKIOCGGEOM
This ioctl is used to get the disk geometry. The
metadisk driver fills in the dkg_nhead, dkg_nsect,
dkg_rpm, dkg_write_reinstruct and dkg_read_reinstruct
from the first component of the metadevice (at
metainit time). dkg_ncyl is calculated using the size
of the metadevice (reported by metastat) divided by
(dkg_nhead * dkg_nsect). The total size is always a
multiple of (dkg_nhead * dkg_nsect). If the first com-
ponent of a metadevice does not start on cylinder
number 0, then the dkg_ncyl 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 metadevice
is not set up, then ENXIO is returned.
DKIOCINFO
When issued to the administrative device or metadev-
ice, this ioctl sets dki_unit to the unit number of
the metadevice, dki_ctype to a value of DKC_MD, and
dki_partition 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.
v_nparts is always 1. v_part[0].p_start is 0 if the
first component of the metadevice starts on cylinder
0. Otherwise, the p_start field is the starting sector
of cylinder 1. v_part[0].p_size 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
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 prop_op entry point.
md: db: Parsing error on 'dev'
Set command in /kernel/drv/md.conf for the mddb.bootlist
<number> 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: dnum: not configurable, check /kernel/drv/md.conf
This error occurs when the number of metadevices as speci-
fied by the nmd parameter in the /kernel/drv/md.conf file is
lower than the number of configured metadevices on the sys-
tem. It can also occur if the md_nsets parameter for
disksets is lower than the number of configured disksets on
the system. To fix this problem, examine the md.conf file
and increase the value of either nmd or md_nsets as needed.
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
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
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/d n
block device (where n is the device number)
/dev/md/rdsk/d n
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/md_stripe
stripe driver misc module
/kernel/misc/md_mirror
mirror driver misc module
/kernel/misc/md_hotspares
hotspares driver misc module
/kernel/misc/md_trans
metatrans driver for UFS logging
/kernel/misc/md_raid
RAID5 driver misc module
SEE ALSO
metaclear(1M), metadb(1M), metadetach(1M), metahs(1M),
metainit(1M), metaoffline(1M), metaonline(1M),
metaparam(1M), metareplace(1M), metaroot(1M), metastat(1M),
metasync(1M), metattach(1M), dkio(7I), md.tab(4), md.cf(4),
mddb.cf(4)
Solaris Volume Manager Administration Guide
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