Use the rmnodecanister command to delete
a node canister from the clustered system (system). Enter
this command at any time after a system has been created.
Syntax
rmnodecanister
[ -force ]
{
object_id | object_name }
Parameters
- -force
- (Optional) Overrides
the checks that this command runs. The parameter overrides the following
two checks:
- If the command results in volumes going offline, the
command fails unless the force parameter is used.
- If the command results in a loss of data because there is unwritten
data in the write cache that is contained only within the node canister
to be removed, the command fails unless the force parameter is used.
If you use the force parameter as a result
of an error about volume going offline, you force the node
canister removal and run the risk of losing data from the write cache.
The force parameter should always be used with
caution.
- object_id | object_name
- (Required) Specifies the object name or ID that
you want to modify. The variable that follows the parameter is either:
- The object name that you assigned when you added the node to the
clustered system
- The object ID that is assigned to the node - not the worldwide
node name (WWPN)
Description
This command removes a node canister from the system.
This makes the node canister a candidate to be added back into this system or into another system. After the node canister
is deleted, the other canister in the I/O group enters write-through
mode until another canister is added back into the I/O group.
Attention: When you run the
rmnodecanister command to remove the configured hardware for a node canister:
- Small Computer System Interface-3 (SCSI-3) reservations (through
that node canister) are removed
- Small Computer System Interface-3 (SCSI-3) registrations (through
that node canister) are removed
By default, the rmnodecanister command
flushes the cache on the specified canister before the canister is
taken offline. In some circumstances, such as when the system is already
degraded (for example, when both canisters in the I/O group are online
and the volumes within the I/O group are degraded), the system ensures
that data loss does not occur as a result of deleting the only canister
with the cache data.
The cache is flushed before the canister
is deleted to prevent data loss if a failure occurs on the other canister
in the I/O group.
Run the rmnodecanister command
with the force parameter to take the specified
node canister offline immediately without flushing the cache (while
ensuring that there is no data loss).
Attention: These prerequisites should be considered:
Before you issue
the rmnodecanister command, perform the following
tasks and read the following Attention notices to avoid losing access
to data:
- Determine which volumes are still assigned to this I/O
group by issuing the following command. The command requests a filtered
view of the volume, where the filter attribute is the I/O
group.
lsvdisk -filtervalue IO_group_name=name
where name is the name of the I/O group. Note: Any volumes that are assigned to the
I/O group that this node canister belongs to are assigned
to the other canister in the I/O group; the preferred canister
is changed. You cannot change this setting back.
- Determine the hosts that the volumes are mapped to by
issuing the lsvdiskhostmap command.
- Determine if any of the volumesthat are assigned
to this I/O group contain data that you need to access:
- If you do not want to maintain access to these volumes, go to step 5.
- If you do want to maintain access to some or
all of the volumes, back up the data or migrate the data
to a different (online) I/O group.
- Determine if you need to turn the power off to the node:
- If this is the last node canister in the system, you
do not need to turn the power off to the node. Go to step 5.
- If this is not the last node canister in
the system, turn the power off to the canister that you intend
to remove. This step ensures that the Subsystem Device Driver
(SDD) does not rediscover the paths that are manually removed before
you issue the delete canister request.
- Update the SDD configuration for each
virtual path (vpath) that is presented by the volumes that
you intend to remove. Updating the SDD configuration removes the vpaths
from the volumes. Failure to update the configuration can
result in data corruption. See the Multipath Subsystem Device
Driver: User's Guide for details about how to dynamically
reconfigure SDD for the given host operating system.
- Quiesce all I/O operations that are destined for the node canister that you are deleting. Failure to quiesce the operations can result in failed I/O operations being reported to your host
operating systems.
Attention:
- Removing the last node canister in the system destroys
the system. Before you delete the last node canister in the system, ensure that you want to destroy the system.
- If you are removing a single node canister and the remaining canister
in the I/O group is online, the data can be exposed to a single point
of failure if the remaining canister fails.
- This command might take some time to complete since the cache
in the I/O group for that node canister is flushed before the canister
is removed. If the force parameter is used, the
cache is not flushed and the command completes more quickly. However,
if the deleted canister is the last canister in the I/O group, using
the force option results in the write cache for
that canister being discarded rather than flushed, and data loss can
occur. Use the force option with caution.
- If both nodes in the I/O group are online and the volumes are already degraded before deleting the node, redundancy to the volumes is already degraded and loss of access to data and loss
of data might occur if the force option is used.
Notes:
- If you are removing the configuration node, the rmnodecanister command causes the configuration node canister to move to a different
canister within the system. This process might take a short
time: typically less than a minute. The system IP address
remains unchanged, but any SSH client attached to the configuration
node canister might need to reestablish a connection. The management GUI reattaches to the new configuration node canister transparently.
- If this is the last node canister in the system or if
it is currently assigned as the configuration node, all connections
to the cluster are lost. The user interface and any open CLI sessions
are lost if the last canister in the system is deleted. A
time-out might occur if a command cannot be completed before the node
canister is deleted.
An invocation example for rmnodecanister
rmnodecanister 1
The resulting output
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