md(7D)								      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  Trans devices are no longer supported and have been replaced by UFS logging. See mount_ufs(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 sin-
       gle read or write call usually results in one I/O operation; raw I/O is therefore considerably more efficient when many bytes are transmit-
       ted.  The names of the block devices are found in /dev/md/dsk; the names of the raw devices are found in /dev/md/rdsk. Metadevices 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 metadevice, such as /dev/md/rdsk/d0. See dkio(7i) 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 component 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 metadevice, 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 missing, 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 mirror 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 mirror 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

       A read or write error has occurred on the specified submirror, 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 submirror, 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. Otherwise 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 mod-
       ule 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/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/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

       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. Existing trans devices are not logging--they pass data directly through to the under-
       lying device. See mount_ufs(1M) for more information about UFS logging.

SunOS 5.10							    29 Aug 2003 							    md(7D)