admmdisk(1M) DG/UX 5.4 Rel. 2.01 admmdisk(1M)
NAME
admmdisk - manage software mirrored disks
SYNTAX
admmdisk -o list [ -qvi ] [ name ... ]
admmdisk -o create [ -m minimumimagesrequiredforuse ] [ -an ] {
-I imagelist } ... newname
admmdisk -o supplement { -I imagelist } ... name
admmdisk -o break [ -I imagelist ] ... name
admmdisk -o break name ...
admmdisk -o synchronize [ -lq ] -s sourceimage -d destinationimage
DESCRIPTION
The admmdisk command manages software mirrored disks ("mirrors"). A
mirror functions like a logical disk, but can have its data
replicated ("mirrored") in several places ("images"), to enhance
performance and/or reliability. To achieve these goals, the images
of a mirror should be on separate physical disks (it's even better if
separate controllers are used), but currently the software does not
enforce this requirement. The images of a mirror must all be the
same size. Currently, a maximum of three images are allowed, but
this may change in a future release of DG/UX.
Currently, each image of a mirror must be a logical disk (see
admldisk(1M)). This may change in a future release of DG/UX.
For each mirror, a count of the minimum number of images that is
required for the mirror to be considered "usable" may be specified.
When a mirror is "unusable", attempts to mount(2) or open(2) the
mirror will fail. When the system is brought up, a mirror will
remain unusable until at least the specified number of images of the
mirror are available (i.e. the physical disks containing all the
pieces of the image are registered, and the image is either in sync
or being synced). By default, the minimum required images count is
one. This count must be greater than zero and less than or equal to
the maximum number of images that a mirror can possibly have. Note
that the count need not be less than or equal to the number of images
that the mirror actually has.
Depending upon the circumstances of their last modification, images
of a mirror may be "in sync" or "out of sync". When the system is
brought up, it can recognize these conditions. "Synchronizing" a
mirror consists of copying the whole contents of one image onto the
out-of-date image(s). For a large mirror, this can take a
significant amount of time.
For each mirror, automatic synchronization may be enabled or
disabled. When the system is brought up, the images of the mirror
are inspected to determine if they are "in sync" with each other. If
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they are not in sync, and auto-sync is enabled, the most recently
updated image of the mirror is copied to the out-of-sync image(s).
If there are not enough images in sync to satisfy the minimum-images
requirement, and auto-sync is disabled, the system administrator must
manually invoke the synchronize operation before the mirror will be
usable.
The only way to modify the minimum image count and auto-synchronize
values for a mirror is to delete (break all the images off of) the
mirror, and re-create it.
Each logical disk normally has a corresponding entry in the
directories /dev/dsk and /dev/rdsk. When a logical disk is
incorporated into a mirror (made an image of the mirror), that entry
is removed. When a mirror is created, an entry for the mirror
appears in /dev/dsk and /dev/rdsk.
Operations
list Displays information about one or more mirror(s). By
default, the output consists of one line for each mirror
specified on the command line (if no mirrors are specified,
all mirrors on the system are listed). This lines
includes:
the name of the mirror,
the size of the mirror in blocks (the size of each
image, not the total disk space consumed by all
images),
the number of images currently present,
the number of images required to use the mirror, and
whether or not automatic synchronization is enabled.
Note that even if an image is present, it will not count
towards the number of images required to use the mirror if
it is out of sync and not currently being synced.
If the -i (images) option is specified, then in addition to
the one line for each mirror, one line is produced for each
image in each mirror that is listed. This lines includes:
the name of the logical disk on which the image is
stored,
an indication as to whether the image is up to date,
out of date, being synchronized, or being used as a
synchronization master (which implies that it is up to
date), and
the name of the physical disk upon which the first
piece of the logical disk is stored.
create Creates a new mirror out of the image(s) (logical disks)
specified with -I option(s). At least one image must be
specified. Newname must not be the name of an existing
mirror or logical disk extant on any currently-registered
physical disk, and must be made up of printing characters
(as defined by isprint(1)), and may not include any of the
characters ( ) / + : space or tab. The mirror is actually
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created by adding the images one after another. If the
first image is added successfully, and then an error occurs
while adding a subsequent image, the mirror may be left in
place with only some of the images specified with -I
options.
supplement
Adds the image(s) specified with -I option(s) to the
specified mirror, which must already exist.
break Breaks image(s) off an existing mirror. This may be used
to either break all images off of one or more mirrors, or
to break one or more specific images off of one mirror. If
no images are specified (with the -I option), all the
images are broken off the specified mirror(s). As each
image is broken off of the mirror, entries for the
corresponding logical disk appear in /dev/dsk and
/dev/rdsk. When the last image is broken off the mirror,
the mirror ceases to exist, and the entries in /dev/dsk and
/dev/rdsk for it are removed. Currently, if a synchronize
operation (either explicitly requested or automatically
initiated) is underway, no image can be broken off the
mirror. This may change in a future release of DG/UX.
synchronize
Copies the whole contents of sourceimage to
destinationimage. Synchronize can be abbreviated to sync.
Options
The following options can be used with the list operation:
-q Quiet. Causes the output of the list operation to not have
any headers, and to have fields be separated with colons
rather than white space.
-v Verbose. This is the default.
-i Images. Causes the output to include one line per mirror
image, as described above.
The following options can be used with the create operation:
-m minimumimagesrequiredforuse
Minimum image count. This specifies the minimum number of
images of the mirror that must be present and either in
sync or being synchronized for the mirror to be considered
usable.
-a Automatic synchronization. This is the default.
-n No automatic synchronization.
The following option is used with the create, supplement, and break
operations:
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-I imagelist
Image name(s). Specifies that the logical disk(s) in
imagelist are to be made part of (create and supplement)
or removed from (break) the mirror. Multiple images may be
specified either by using multiple -I options, or by
providing a comma-separated list of names with a single -I.
The following options can be with the synchronize operation.
-l Lazy. The copy operation is done slowly, to reduce
interference with other system operations. The default is
to copy the images as quickly as possible.
-q Quiet. The user is not asked to confirm before the
operation is performed.
-s sourceimage
The mirror image to use as the source of the synchronize
operation.
-d destinationimage
The image to use as the destination of the synchronize
operation.
DIAGNOSTICS
Exit Codes
0 The operation was successful.
1 The operation was unsuccessful.
2 The operation failed due to access restrictions.
3 There was an error in the command line.
SEE ALSO
admldisk(1M), admpdisk(1M), mkfs(1M).
NOTES
Anomalies (including the loss of data) can occur if any operation on
a mirror is performed while a physical disk that contains a related
mirror image is unregistered. Admmdisk cannot prevent these
anomalies. See Managing the DG/UX System for further details on
this.
The design of the logical disk and mirror subsystem may change in a
future release of DG/UX.
The name all is reserved, you may not create a software mirrored disk
by that name.
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