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NetApp Protecting SVM Root Volume
For any data Storage Virtual Machines (SVMs) that have a namespace (CIFS and/or NFSv3), it is recommended to protect the SVM root volume. This is not required for SAN based (FC or iSCSI only).
There are two ways to accomplish this: Data Protection Mirrors (DP) or Load-Sharing Mirrors (LS). Original best practices recommended these mirrors of the SVM root volume should be placed on every node, including the node where the source volume resides, in the cluster. However, the updated recommendation is to have two. If you have a 2-Node cluster then both nodes would require the mirror. If you have a 4-Node or larger cluster, it is recommended to separate the mirrors on different HA pairs within the cluster.
While both DP and LS mirrors accomplish the same end result of protecting the SVM root volume, there are some operational differences that you must be aware of when using them.
The first difference, if the decision is to use LS mirrors, is an extra step that must be performed to update the namespace. Changes with shares, exports or new volumes will not be immediately reflected in the namespace. Updating a LS mirror set is required if you want these namespace changes reflected and visible to all clients.
Another key difference between DP and LS mirrors are LS mirrors do not work for NFSv4. Red8 recommends the use of DP mirrors instead of LS mirrors only if the cluster is licensed for SnapMirror.
Restoring a SVM’s Root Volume
Regardless if you decide to use DP mirrors or LS mirrors to protect the SVM root volume, the restoration procedure is rather simple. Review the NetApp article Restoring a Vserver’s root volume.
Creating DP Mirror for SVM Root
- Create Target Volumes – Start by creating the target volumes for the mirrors. The first mirror should be on the same aggregate as the source root volume. If this is a 4-Node or larger cluster, make sure that you have the destination mirrors on separate HA pairs.
cluster1::> volume create -vserver vs1 -volume vs1_root_DP01 -aggregate cluster1_01_aggr0 -size 1g -type DP
cluster1::> volume create -vserver vs1 -volume vs1_root_DP02 -aggregate cluster1_02_aggr0 -size 1g -type DP- Create DP Mirror Relationship
cluster1::> snapmirror create -source-path vs1:vs1_root -destination-path vs1:vs1_root_DP01 -type DP -schedule hourly
cluster1::> snapmirror create -source-path vs1:vs1_root -destination-path vs1:vs1_root_DP02 -type DP -schedule hourly- Initialize DP Mirror Relationship
cluster1::> snapmirror initialize -destination-path vs1:vs1_root_DP*- Validate DP Mirror Relationship
cluster1::> snapmirror show -destination-path vs1:vs1_root_DP*Creating LS Mirror for SVM Root
- Create Target Volumes – Start by creating the target volumes for the mirrors. The first mirror should be on the same aggregate as the source root volume. If this is a 4-Node or larger cluster, make sure that you have the destination mirrors on separate HA pairs.
cluster1::> volume create -vserver vs1 -volume vs1_root_LS01 -aggregate cluster1_01_aggr0 -size 1g -type DP
cluster1::> volume create -vserver vs1 -volume vs1_root_LS02 -aggregate cluster1_02_aggr0 -size 1g -type DP- Create LS Mirror Relationship
cluster1::> snapmirror create -source-path vs1:vs1_root -destination-path vs1:vs1_root_LS01 -type LS -schedule hourly
cluster1::> snapmirror create -source-path vs1:vs1_root -destination-path vs1:vs1_root_LS02 -type LS -schedule hourly- Initialize LS Mirror Relationship
cluster1::> snapmirror initialize-ls-set vs1:root- Validate LS Mirror Relationship
cluster1::> snapmirror show -destination-path vs1:vs1_root_LS*- Updating LS Mirror Set – This should be performed immediately after any changes to the namespace have been made (shares, exports, volumes). If not performed, the changes will not be reflected in the namespace until after the next scheduled update.
cluster1::> snapmirror update-ls-set -source-path vs1:root