Administrator Guide
Table Of Contents
- Dell EMC Storage Systems Administrator Guide for PowerStore and Unity XT metro node feature
- CLI Workspace and User Accounts
- Meta Volumes
- System Management
- Thin support in metro node
- Provisioning Storage
- Volume expansion
- Data migration
- About data migrations
- Migrating thin-capable storage
- About rebuilds
- One-time data migrations
- Batch migrations
- Prerequisites
- Creating a batch migration plan
- Checking a batch migration plan
- Modifying a batch migration file
- Starting a batch migration
- Pausing/resuming a batch migration (optional)
- Canceling a batch migration (optional)
- Monitoring a batch migration’s progress
- Viewing a batch migration’s status
- Committing a batch migration
- Cleaning a batch migration
- Removing batch migration records
- Configure the WAN Network
- Consistency Groups
- Performance and Monitoring
- Metro node with active-passive storage arrays
- Index
Detach-rule
Detach rules are a consistency group’s policy for automatically picking a winning cluster when there is an inter-cluster link
outage.
For metro node Metro configurations, there are two consistency group detach rules:
● no-automatic-winner - The consistency group does not select a winning cluster.
● winner cluster-name delay seconds - The cluster specified by cluster-name is declared the winner if an inter-
cluster link outage lasts more than the number of seconds specified by delay.
If a consistency group has a detach rule configured, the rule applies to all volumes in the consistency group and overrides any
rule-sets applied to individual volumes.
This property is not applicable for local consistency groups.
By default, no specific detach rule is configured for a consistency group. Instead, the no-automatic-winner detach rule is
set as default for a consistency group with visibility to both clusters.
Best practice is to apply detach rules to a consistency group that meet the needs of your application in terms of I/O
continuance and data loss tolerance.
Use the consistency-group set-detach-rule commands to configure the detach-rule for a consistency group:
● Use the consistency-group set-detach-rule no-automatic-winner command to set the detach-rule as no-
automatic-winner:
VPlexcli:/clusters/cluster-1/consistency-groups/TestCG> set-detach-rule no-automatic-
winner
● Use the consistency-group set-detach-rule winner command to specify which cluster is the winner, and the
number of seconds metro node waits after a link outage before detaching the winning cluster:
VPlexcli:/clusters/cluster-1/consistency-groups/TestCG> set-detach-rule winner --
cluster cluster-1 --delay 5s
The following table describes the detach rule behavior for synchronous consistency group.
Table 9. Detach rule behavior - synchronous consistency group
Detach rule Behavior (irrespective of the cluster on which I/O is
happening)
Cluster-1 wins I/O is allowed on Cluster-1
I/O suspends at Cluster-2
No data loss / no data rollback
Cluster-2 wins I/O suspends at Cluster-1
I/O is allowed on Cluster-2
No data loss / no data rollback
No automatic winner
a
I/O suspends at Cluster-1
I/O suspends at Cluster-2
No data loss / no data rollback
a.
DU on both clusters if WAN-COM connectivity between metro node clusters goes down
Note the following:
● Active I/O indicates active writes.
● The detach rule behavior described the previous table are based on the assumption that there is a healthy leg in the winner
cluster, during the time of cluster partition.
● Use the consistency-group resume-after-rollback command to resume after roll back.
● In case of detach rule no-automatic-winner, to resume I/O, you must manually choose a cluster as the winner. Use the
consistency-group choose-winner command to choose a winner.
64
Consistency Groups