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Depending on the administrator’s requirements, archiving snapshots may be required on the target cluster. Configuring snapshot archival on the target cluster is an optional configuration, as displayed in the following figure.
By default, if the Enable capture of snapshots on the target cluster is not selected, the target cluster only retains the most recent snapshot, which is used during a failover.
To enable snapshot archiving on the target cluster, a SnapshotIQ license is required. When SyncIQ policies are set with snapshots on the target cluster, on the initial sync a snapshot will be taken at the beginning and the end. For incremental syncs, a snapshot will only be taken at the completion of the job.
Note: Before initializing a job, SyncIQ checks for the SnapshotIQ license on the target cluster. If it has not been licensed, the job will proceed without generating a snapshot on the target cluster, and SyncIQ will issue an alert noting that the license was not available.
Administrators can control how many snapshots of the target replication path are maintained over time by defining an expiration period on each of the target-cluster snapshots. For example, if a replication job is performed every day for a week (with target snapshots enabled), seven snapshots of the dataset on the target cluster are available, representing seven available versions of the dataset. In this example, if the target-cluster snapshot is configured to expire after seven days on a replication policy that is run once per day, only seven snapshots will be available on the target cluster dataset.
Note: If snapshot-based replication is configured as explained in Whenever a snapshot of the source directory is taken and in SnapshotIQ and SyncIQ, target snapshot archival may be a necessity. If target snapshots are not archived, a separate snapshot copy is not retained when a new snapshot becomes available.
For more information about snapshots and SyncIQ, reference SnapshotIQ and SyncIQ and Snapshots and SyncIQ policies.
Snapshot aliasing on a target cluster provides a powerful option for accessing SyncIQ based snapshots directly on a target cluster. A Snapshot Alias is recommended for scenarios where a workflow requires access to the most current snapshot on the target cluster and a consistent snapshot name. After a SyncIQ policy is configured on the source cluster with a Snapshot Alias, an NFS export may be configured on the target cluster, pointing directly to the Snapshot Alias.
If a workflow uses the HEAD snapshot, or the most recent SyncIQ snapshot, errors occur if the snapshot is accessed directly when a SyncIQ job is running. The errors occur because the HEAD SyncIQ snapshot is in the process of updating.
Note: As a best practice, accessing SyncIQ based snapshots for client access is not recommended. For client access, a Snapshot Alias should be configured with an NFS export pointing to the Snapshot Alias.
To create or modify an existing SyncIQ policy with a snapshot alias on the target cluster, perform the following steps:
isi sync policies create [Policy Name] sync --source-root-path=[Source Cluster Rooth Path] --target-host=[Target Cluster IP] --target-path=[Target Cluster Directory] --target-snapshot-archive=true --target-snapshot-alias=example_sync_snap
In the preceding example, the snapshot alias is defined as example_sync_snap.
Alternatively, to modify an existing SyncIQ policy on the source cluster:
isi sync policies modify [Policy Name] --target-snapshot-archive=true --target-snapshot-alias=example_sync_snap
Note: As a best practice, consider configuring a target snapshot expiration date that is reasonable for the workflow. The target snapshot expiration is configured using the --target-snapshot-expiration option in the CLI. This parameter specifies the expiration in seconds.
isi nfs exports create --paths=[Target Cluster Directory defined in SyncIQ policy in step 1] --snapshot=example_sync_snap
Linux-client# mount [Target cluster IP]:[Target Cluster Directory defined in step 1] [Specify local mount location]
Alternatively, for a Microsoft Windows 10 client, enable the NFS service under Control Panel > Programs > Programs and Features > Turn Windows features on or off. Enable Services for NFS and mount the export from the Windows command prompt:
mount \\[Target Cluster IP]\[Target Cluster Directory defined in step 1] [Select a drive to map this mount]
As each new SyncIQ policy runs, the Snapshot Alias continues to point to the newest or HEAD SyncIQ snapshot. The Snapshot Alias pointer can be confirmed by listing the snapshot details. To check the snapshot details, perform the following steps:
isi9-s2-n1-1# isi snapshot snapshots list
ID Name Path
----------------------------------------------------------
2 SIQ-isi9-s1-n1-foo-2020-06-25_11-08-10 /ifs/data/cls1
3 example_sync_snap /ifs/data/cls1
5 SIQ-Failover-foo-2020-06-25_11-08-14 /ifs/data/cls1
----------------------------------------------------------
Total: 3
In this example, the snapshot example_sync_snap is the Snapshot Alias defined in the SyncIQ policy on the source cluster.
isi9-s2-n1-1# isi snapshot snapshots view 3
ID: 3
Name: example_sync_snap
Path: /ifs/data/cls1
Has Locks: No
Schedule: -
Alias Target ID: 2
Alias Target Name: SIQ-isi9-s1-n1-foo-2020-06-25_11-08-10
Created: 2020-06-25T11:08:13
Expires: -
Size: 4.00k
Shadow Bytes: 0.00
% Reserve: 0.00%
% Filesystem: 0.00%
State: active
Currently, the Snapshot Alias is pointing to the Alias Target ID 2. After the SyncIQ policy is run again, the snapshots list is updated with the new snapshot:
isi9-s2-n1-1# isi snapshot snapshots list
ID Name Path
----------------------------------------------------------
2 SIQ-isi9-s1-n1-foo-2020-06-25_11-08-10 /ifs/data/cls1
3 example_sync_snap /ifs/data/cls1
7 SIQ-Failover-foo-2020-06-25_11-15-28 /ifs/data/cls1
9 SIQ-isi9-s1-n1-foo-2020-06-25_11-15-31 /ifs/data/cls1
----------------------------------------------------------
Total: 4
isi9-s2-n1-1# isi snapshot snapshots view 3
ID: 3
Name: example_sync_snap
Path: /ifs/data/cls1
Has Locks: No
Schedule: -
Alias Target ID: 9
Alias Target Name: SIQ-isi9-s1-n1-foo-2020-06-25_11-15-31
Created: 2020-06-25T11:08:13
Expires: -
Size: 4.00k
Shadow Bytes: 0.00
% Reserve: 0.00%
% Filesystem: 0.00%
State: active
The Snapshot Alias is now pointing the Alias Target ID 9, which is the newest, or HEAD snapshot.