metaset(1M)
NAME
metaset - configure shared disksets
SYNOPSIS
/usr/sbin/metaset -s setname [-M] -a -h hostname...
/usr/sbin/metaset -s setname -A {enable | disable}
/usr/sbin/metaset -s setname [-A {enable | disable}] -a -h
hostname...
/usr/sbin/metaset -s setname -a -h hostname...
/usr/sbin/metaset -s setname -a [-l length] drivename...
/usr/sbin/metaset -s setname -d [-f] -h hostname...
/usr/sbin/metaset -s setname -d [-f] drivename...
/usr/sbin/metaset -s setname -r
/usr/sbin/metaset [-s setname] -j
/usr/sbin/metaset [-s setname] -w
/usr/sbin/metaset -s setname -t [-f]
/usr/sbin/metaset -s setname -b
/usr/sbin/metaset -s setname -P
/usr/sbin/metaset -s setname -o [-h hostname]
/usr/sbin/metaset [-s setname]
/usr/sbin/metaset [-s setname] -a | -d [ [m]
mediator_host_list]
DESCRIPTION
In a traditional disk set configuration, multiple hosts are
physically connected to the same set of disks. When one host
fails, the other host has exclusive access to the disks. The
metaset command administers sets of disks shared for
exclusive (but not concurrent) access among such hosts.
While disk sets enable a high-availability configuration,
Solaris Volume Manager itself does not actually provide a
high-availability environment.
A single-node disk set configuration manages storage on a
SAN or fabric-attached storage, or provides namespace con-
trol and state database replica management for a specified
set of disks.
A multi-node disk set configuration, created with the -M
option to metaset, provides for a disk set with shared own-
ership among multiple hosts. All owners can simultaneously
access disks in the set. This option exists to support
high-availability applications and does not attempt to pro-
tect against overlapping writes. Protection against overlap-
ping writes is the responsibility of the application that
issues the writes. Multi-node disk sets do not support RAID
5 volumes or transactional volumes (trans metadevices).
Shared metadevices and hot spare pools can be created only
from drives which are in the disk set created by metaset. To
create a set, one or more hosts must be added to the set. To
create metadevices within the set, one or more devices must
be added to the set. The drivename specified must be in the
form cxtxdx with no slice specified.
When you add a new disk to any disk set, Solaris Volume
Manager checks the disk format. If necessary, it reparti-
tions the disk to ensure that the disk has an appropriately
configured reserved slice (slice 7 on a VTOC labelled device
or slice 6 on an EFI labelled device), with adequate space
for a state database replica. The precise size of slice 7
(or slice 6 on an EFI labelled device), depends on the disk
geometry. For traditonal disk sets, the slice is no less
than 4 Mbytes, and probably closer to 6 Mbytes, depending on
where the cylinder boundaries lie. For multi-node disk sets,
the slice is a minimum of 256 Mbytes.
The minimal size for the reserved slice might change in the
future. This change is based on a variety of factors,
including the size of the state database replica and infor-
mation to be stored in the state database replica.
For use in disk sets, disks must have a dedicated slice (six
or seven) that meets specific criteria:
o Slice must start at sector 0
o Slice must include enough space for disk label
o State database replicas cannot be mounted and does not
overlap with any other slices, including slice 2
If the existing partition table does not meet these cri-
teria, Solaris Volume Manager repartitions the disk. A por-
tion of each drive is reserved in slice 7 (or slice 6 on an
EFI labelled device), for use by Solaris Volume Manager. The
remainder of the space on each drive is placed into slice 0.
Any existing data on the disks is lost by repartitioning.
After you add a drive to a disk set, it might be reparti-
tioned as necessary, with the exception that slice 7 (or
slice 6 on an EFI labelled device), is not altered in any
way.
After a disk set is created and metadevices are set up
within the set, the metadevice name is in the following
form:
/dev/md/setname/{dsk,rdsk}/dnumber
where setname is the name of the disk set, and number is the
number of the metadevice (0-127).
Hot spare pools within local disk sets use standard Solaris
Volume Manager naming conventions. Hot spare pools with
shared disk sets use the following convention:
setname/hspnumber
where setname is the name of the disk set, and number is the
number of the hot spare pool (0-999).
Mediator Configuration
SVM provides support for a low-end HA solution consisting of
two hosts that share only two strings of drives. The hosts
in this type of configuration, referred to as mediators or
mediator hosts, run a special daemon, rpc.metamedd(1M). The
mediator hosts take on additional responsibilities to ensure
that data is available in the case of host or drive
failures.
A mediator configuration can survive the failure of a single
host or a single string of drives, without administrative
intervention. If both a host and a string of drives fail
(multiple failures), the integrity of the data cannot be
guaranteed. At this point, administrative intervention is
required to make the data accessible. See mediator(7D) for
further details.
Use the -m option to add or delete a mediator host.
OPTIONS
The following options are supported:
-a Adds drives or hosts to the named set. For a drive to
be accepted into a set, the drive must not be in use
within another metadevice or disk set, mounted on, or
swapped on. When the drive is accepted into the set,
it is repartitioned and the metadevice state database
replica (for the set) can be placed on it. However, if
a slice 7 (or slice 6 on an EFI labelled device),
starts at cylinder 0, and is large enough to hold a
state database replica, then the disk is not repar-
tioned. Also, a drive is not accepted if it cannot be
found on all hosts specified as part of the set. This
means that if a host within the specified set is
unreachable due to network problems, or is administra-
tively down, the add fails.
-a -d -m mediator_host_list
Adds (-a) or deletes (-d) mediator hosts to the speci-
fied disk set. A mediator_host_list is the nodename(4)
of the mediator host to be added and (for adding) up
to two other aliases for the mediator host. The
nodename and aliases for each mediator host are
separated only by commas. Up to two mediator hosts can
be specified for the named disk set. For deleting a
mediator host, specify only the nodename of that host
as the option to -m.
In a single metaset command you can add or delete two
mediator hosts. See EXAMPLES.
-A {enable | disable}
Specify auto-take status for a disk set. If auto-take
is enabled for a set, the disk set is automatically
taken at boot, and file systems on volumes within the
disk set can be mounted through /etc/vfstab entries.
Only a single host can be associated with an auto-take
set, so attempts to add a second host to an auto-take
set or attempts to configure a disk set with multiple
hosts as auto-take fails with an error message. Disa-
bling auto-take status for a specific disk set causes
the disk set to revert to normal behavior. That is,
the disk set is potentially shared (non-concurrently)
among hosts, and unavailable for mounting through
/etc/vfstab.
-b Insures that the replicas are distributed according to
the replica layout algorithm. This can be invoked at
any time, and does nothing if the replicas are
correctly distributed. In cases where the user has
used the metadb command to manually remove or add
replicas, this command can be used to insure that the
distribution of replicas matches the replica layout
algorithm.
-C {take | release | purge}
Do not interact with the Cluster Framework when used
in a Sun Cluster 3 environment. In effect, this means
do not modify the Cluster Configuration Repository.
These options should only be used to fix a broken disk
set configuration.
This option is not for use with a multi-node disk set.
take Take ownership of the disk set but do not inform
the Cluster Framework that the disk set is
available
release
Release ownership of the disk set without
informing the Cluster Framework. This option
should only be used if the disk set ownership
was taken with the corresponding -C take option.
purge Remove the disk set without informing the Clus-
ter Framework that the disk set has been purged
-d Deletes drives or hosts from the named disk set. For a
drive to be deleted, it must not be in use within the
set. The last host cannot be deleted unless all of the
drives within the set are deleted. Deleting the last
host in a disk set destroys the disk set. This option
fails on a multi-node disk set if attempting to with-
draw the master node while other nodes are in the set.
-f Forces one of three actions to occur: takes ownership
of a disk set when used with -t; deletes the last disk
drive from the disk set; or deletes the last host from
the disk set. (Deleting the last drive or host from a
disk set requires the -d option.) When used to forci-
bly take ownership of the disk set, this causes the
disk set to be grabbed whether or not another host
owns the set. All of the disks within the set are
taken over (reserved) and fail fast is enabled, caus-
ing the other host to panic if it had disk set owner-
ship. The metadevice state database is read in by the
host performing the take, and the shared metadevices
contained in the set are accessible. The -f option is
also used to delete the last drive in the disk set,
because this drive would implicitly contain the last
state database replica. The -f option is also used for
deleting hosts from a set. When specified with a par-
tial list of hosts, it can be used for one-host
administration. One-host administration could be use-
ful when a host is known to be non-functional, thus
avoiding timeouts and failed commands. When specified
with a complete list of hosts, the set is completely
deleted. It is generally specified with a complete
list of hosts to clean up after one-host administra-
tion has been performed.
-h hostname...
Specifies one or more host names to be added to or
deleted from a disk set. Adding the first host creates
the set. The last host cannot be deleted unless all of
the drives within the set have been deleted. The host
name is not accepted if all of the drives within the
set cannot be found on the specified host. The host
name is the same name found in /etc/nodename.
-j Joins a host to the owner list for a multi-node disk
set. The concepts of take and release, used with trad-
itional disk sets, do not apply to multi-node sets,
because multiple owners are allowed. As a host boots
and is brought online, it must go through three confi-
guration levels to be able to use a multi-node set.
First, it must be included in the cluster nodelist,
which happens automatically in a cluster or single-
node sitatuion. Second, it must be added to the
multi-node disk set with the -a -h options documented
elsewhere in this man page. Finally, it must join the
set. When the host is first added to the set, it is
automatically joined. On manual restarts, the adminis-
trator must manually issue metaset -s multinodesetname
-j to join the host to the owner list. After the clus-
ter reconfiguration, when the host reenters the clus-
ter, the node is automatically joined to the set. The
metaset -j command joins the host to all multi-node
sets that the host has been added to. In a single node
situation, joining the node to the disk set starts any
necessary resynchronizations.
-l length
Sets the size (in blocks) for the metadevice state
database replica. The length can only be set when
adding a new drive; it cannot be changed on an exist-
ing drive. The default (and maximum) size is 8192
blocks, which should be appropriate for most confi-
gurations. The minimum size of the length is 64
blocks.
-M Specifies that the diskset to be created or modified
is a multi-node disk set that supports multiple con-
current owners. The -M option is required when creat-
ing a multi-node disk set, but optional on all other
operations on a multi-node disk set. Existing disk
sets cannot be converted to multi-node sets.
-o Returns an exit status of 0 if the local host or the
host specified with the -h option is the owner of the
disk set.
-P Purge the named disk set from the node on which the
metaset command is run. The disk set must not be owned
by the node that runs this command. If the node does
own the disk set the command fails.
This option is not for use with a multi-node disk set.
-r Releases ownership of a disk set. All of the disks
within the set are released. The metadevices set up
within the set are no longer accessible.
This option is not for use with a multi-node disk set.
-s setname
Specifies the name of a disk set on which metaset
works. If no setname is specified, all disk sets are
returned.
-t Takes ownership of a disk set safely. If metaset finds
that another host owns the set, this host is not
allowed to take ownership of the set. If the set is
not owned by any other host, all the disks within the
set are owned by the host on which metaset was exe-
cuted. The metadevice state database is read in, and
the shared metadevices contained in the set become
accessible. The -t option takes a disk set that has
stale databases. When the databases are stale, metaset
exits with code 66, and prints a message. At that
point, the only operations permitted are the addition
and deletion of replicas. Once the addition or dele-
tion of the replicas has been completed, the disk set
should be released and retaken to gain full access to
the data.
This option is not for use with a multi-node disk set.
-w Withdraws a host from the owner list for a multi-node
disk set. The concepts of take and release, used with
traditional disk sets, do not apply to multi-node
sets, because multiple owners are allowed. Instead of
releasing a set, a host may issue metaset -s multino-
desetname -w to withdraw from the owner list. A host
automatically withdraws on a reboot, but can be manu-
ally withdrawn if it should not be able to use the
set, but should be able to rejoin at a later time. A
host that withdrew due to a reboot may still appear
joined from other hosts in the set until a reconfi-
guration cycle occurs. The command metaset -w with-
draws from ownership of all multinode sets that the
host is a member of. This option fails if attempting
to withdraw the master node while other nodes are in
the disk set owner list. This option cancels all
resyncs running on the node. A cluster reconfiguration
process that is removing a node from the cluster
membership list effectively withdraws the host from
the ownership list.
EXAMPLES
Example 1: Defining a Disk Set
This example defines a disk set.
# metaset -s relo-red -a -h red blue
The name of the disk set is relo-red. The names of the first
and second hosts added to the set are red and blue, respec-
tively. (The hostname is found in /etc/nodename.) Adding the
first host creates the disk set. A disk set can be created
with just one host, with the second added later. The last
host cannot be deleted until all of the drives within the
set have been deleted.
Example 2: Adding Drives to a Disk Set
This example adds drives to a disk set.
# metaset -s relo-red -a c2t0d0 c2t1d0 c2t2d0 c2t3d0 c2t4d0 c2t5d0
The name of the previously created disk set is relo-red. The
names of the drives are c2t0d0, c2t1d0, c2t2d0, c2t3d0,
c2t4d0, and c2t5d0. Note that there is no slice identifier
("sx") at the end of the drive names.
Example 3: Adding Multiple Mediator Hosts
The following command adds two mediator hosts to the speci-
fied disk set.
# metaset -s mydiskset -a -m myhost1,alias1 myhost2,alias2
Example 4: Purging a Disk Set from the Node
The following command purges the disket relo-red from the
node:
# metaset -s relo-red -P
Example 5: Defining a Multi-node Disk Set
This example defines a multi-node disk set.
# metaset -s blue -M -a -h hahost1 hahost2
The name of the disk set is blue. The names of the first and
second hosts added to the set are hahost1 and hahost2,
respectively. The hostname is found in /etc/nodename. Adding
the first host creates the multi-node disk set. A disk set
can be created with just one host, with additional hosts
added later. The last host cannot be deleted until all of
the drives within the set have been deleted.
FILES
/etc/lvm/md.tab
Contains list of metadevice configurations.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
>0 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWmdu |
|_____________________________|_____________________________|
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), md.cf(4), md.tab(4),
mddb.cf(4), attributes(5)
Solaris Volume Manager Administration Guide
NOTES
Disk set administration, including the addition and deletion
of hosts and drives, requires all hosts in the set to be
accessible from the network.
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