Creating Mirrors for Virtual Volumes
Mirroring, or the replication of data, essentially involves writing at least two copies of the data, each to a virtual volume. A mirror provides protection against disk failure by replicating the data written to a virtual volume onto another virtual volume on a different storage server. Network Mirroring is a licensed option of the SANsymphony product.
Before creating mirrors, refer to Sizing a Mirror for important information to know before you begin.
IMPORTANT: Mirror path configurations, such as using specific mirror paths or redundant mirror paths, must be configured prior to creating a mirror. After a mirror configuration exists for a virtual volume, mirror path settings cannot be changed. Refer to Specifying the Mirror Path to configure prior to creating mirrors.
A linear virtual volume may be dynamically transformed into a mirror at any time even while the application server is accessing its data through that linear volume. A tertiary mirror can be created by adding a mirror from a third storage server to an existing mirror. Refer to About Tertiary Mirrors for more information.
Mirrors are created in the standard manner reflected in this Help for AP, MPIO, CP, and Traveller rollback virtual volumes but you must specify the mirror path type of your virtual volumes as described in the procedure below. (Mirroring is not available with dual path storage because SANsymphony software automatically creates a standard mirror for volumes from dual path NMV pools.)
In order to guarantee data integrity, mirrors cannot be created from both static and dynamic disks.
There are two methods for creating mirrors: using the Add Mirror to Virtual Volume dialog box or the drag and drop method from the Virtual Volumes tab. Below are the steps for using the dialog box, refer to Creating Mirrors using Drag and Drop for alternative instructions.
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In the Virtual Volumes tab of SANmanager, open the Virtual Volumes folder in the lower-left pane. You will see a list of virtual volumes.
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Select the virtual volume that you want to mirror (this will be your primary mirror volume), and then select Add Mirror from the shortcut menu. The Add Mirror to Virtual Volume dialog box appears.
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In the Path Options area, select the mirror path.
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Use the Standard option if you do not have AP, MPIO, or CP software on the application servers.
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The 3rd Party AP/MPIO option is used when either qualified non-DataCore Alternate Pathing software or the DataCore MPIO software is installed on the application servers.
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Use the Alternate Pathing option if the DataCore Alternate Pathing software is installed on the application servers. Refer to Virtual Volume Properties to make an AP virtual volume bootable or use the Manual Failback feature. (DataCore AP is an EOL software option.)
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The Cluster Path option typically is used when the application servers have cluster software installed. Refer to About Cluster Path for more information.
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In the Mirror Channel Preferences area, select the channel type. Only valid channels are selectable; invalid options are grayed out.
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In the Mirror Volumes area, select:
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Use existing volumes if you want an existing volume to be used for the mirror.
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Create new NMV volumes from pool in list if you want to create a new NMV and use it for the mirror. Select the appropriate pool from the list box below.
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Click OK.
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Verify any mirror mappings before applying the configuration, refer to Mapping Properties. Mirror paths settings and mappings cannot be changed after applying.
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Apply the configuration.
After creating a mirror, it will go into recovery (this is normal behavior). Do not change the configuration for that virtual volume until the recovery completes.
If other storage servers in the region, who have mirror partners to your volumes, are restarted, then you may see a message on the active storage server informing you that new devices have been discovered and asking if you wish to restart. Click No.
To set additional mirror attributes, such as mirror recovery priority, refer to Changing Attributes of a Mirror. Then the next step is mapping the virtual volume to an application server for use, refer to Mapping Virtual Volumes to Application Servers.