SANtricity 11 Manuals (CA08872-010)

Create asynchronous mirrored pair

To configure asynchronous mirroring, you create a mirrored pair that includes a primary volume on the local array and a secondary volume on the remote array.

Synchronous mirroring is not available on ETERNUS AB6100, AB3100 or HB1x00 series storage system.

Before you begin

Before you create a mirrored pair, meet the following requirements for Unified Manager:

The Web Services Proxy service must be running.
Unified Manager must be running on your local host through an HTTPS connection.
Unified Manager must be showing valid SSL certificates for the storage system. You can accept a self-signed certificate or install your own security certificate using Unified Manager and navigating to Certificate > Certificate Management.

Also be sure to meet the following requirements for storage systems and volumes:

The two storage systems must be discovered in Unified Manager.
Each controller in both the primary array and secondary array must have an Ethernet management port configured and must be connected to your network.
You must know the password for the local and remote storage systems.
You must have enough free capacity on the remote storage system to create a secondary volume equal to or greater than the primary volume that you want to mirror.
Your local and remote storage systems are connected through a Fibre Channel fabric or iSCSI interface.
You have created both the primary and secondary volumes that you want to use in the asynchronous mirror relationship.
The secondary volume must be at least as large as the primary volume.

About this task

The process to create an asynchronous mirrored pair is a multi-step procedure.

Step 1: Create or select a mirror consistency group

In this step, you create a new mirror consistency group or select an existing one. A mirror consistency group is a container for the primary and secondary volumes (the mirrored pair), and specifies the desired resynchronization method (manual or automatic) for all pairs in the group.

Steps

From the Manage page, select the local storage system that you want to use for the source.
Select Actions > Create Asynchronous Mirrored Pair.

The Create Asynchronous Mirrored Pair wizard opens.
Select either an existing mirror consistency group or create a new one.

To select an existing group, make sure An existing mirror consistency group is selected, and then select the group from the table. A consistency group can include multiple mirrored pairs.

To create a new group, do the following:
1. Select A new mirror consistency group, and then click Next.
2. Enter a unique name that best describes the data on the volumes that will be mirrored between the two storage systems. A name can only consist of letters, numbers, and the special characters underscore (_), dash (-), and the hash sign (#). A name may not exceed 30 characters and may not contain spaces.
3. Select the remote storage system on which you want to establish a mirror relationship with the local storage system.
  
  If your remote storage system is password protected, the system prompts for a password.
4. Choose whether you want to synchronize the mirrored pairs manually or automatically:
  - Manual
    Select this option to manually start synchronization for all mirrored pairs within this group. Note that when you want to perform a resynchronization later, you must launch SANtricity System Manager for the primary storage system, and then go to Storage > Asynchronous Mirroring, select the group from the Mirror Consistency Groups tab, and then select More > Manually resynchronize.
  - Automatic
    Select the desired interval in Minutes, Hours, or Days, from the beginning of the previous update to the beginning of the next update. For example, if the synchronization interval is set at 30 minutes, and the synchronization process starts at 4:00 p.m., the next process starts at 4:30 p.m.
5. Select the desired alert settings:
  - For manual synchronizations, specify the threshold (defined by the percentage of the capacity remaining) for when you receive alerts.
  - For automatic synchronizations, you can set three methods of alerting: when the synchronization has not completed in a specific length of time, when the recovery point data on the remote array is older than a specific time limit, and when the reserved capacity is nearing a specific threshold (defined by the percentage of the capacity remaining).

Select Next and go to Step 2: Select the primary volume.

If you defined a new mirror consistency group, Unified Manager creates the mirror consistency group on the local storage system first and then creates the mirror consistency group on the remote storage system. You can view and manage the mirror consistency group by launching SANtricity System Manager for each array.

If Unified Manager successfully creates the mirror consistency group on the local storage system, but fails to create it on the remote storage system, it automatically deletes the mirror consistency group from the local storage system. If an error occurs while Unified Manager is attempting to delete the mirror consistency group, you must manually delete it.

Step 2: Select the primary volume

In this step, you select the primary volume to use in the mirror relationship and allocate its reserved capacity. When you select a primary volume on the local storage system, the system displays a list of all the eligible volumes for that mirrored pair. Any volumes that are not eligible to be used do not display in that list.

Any volumes you add to the mirror consistency group on the local storage system will hold the primary role in the mirror relationship.

Steps

From the list of eligible volumes, select a volume that you want to use as the primary volume, and then click Next to allocate the reserved capacity.
From the list of eligible candidates, select reserved capacity for the primary volume.

Keep the following guidelines in mind:
- The default setting for reserved capacity is 20% of the capacity of the base volume, and usually this capacity is sufficient. If you change the percentage, click Refresh Candidates.
- The capacity needed varies, depending on the frequency and size of I/O writes to the primary volume and how long you need to keep the capacity.
- In general, choose a larger capacity for reserved capacity if one or both of these conditions exist:
  - You intend to keep the mirrored pair for a long period of time.
  - A large percentage of data blocks will change on the primary volume due to heavy I/O activity. Use historical performance data or other operating system utilities to help you determine typical I/O activity to the primary volume.
Select Next and go to Step 3: Select the secondary volume.

Step 3: Select the secondary volume

In this step, you select the secondary volume to use in the mirror relationship and allocate its reserved capacity. When you select a secondary volume on the remote storage system, the system displays a list of all the eligible volumes for that mirrored pair. Any volumes that are not eligible to be used do not display in that list.

Any volumes you add to the mirror consistency group on the remote storage system will hold the secondary role in the mirror relationship.

Steps

From the list of eligible volumes, select a volume that you want to use as the secondary volume in the mirrored pair, and then click Next to allocate the reserved capacity.
From the list of eligible candidates, select reserved capacity for the secondary volume.

Keep the following guidelines in mind:
- The default setting for reserved capacity is 20% of the capacity of the base volume, and usually this capacity is sufficient. If you change the percentage, click Refresh Candidates.
- The capacity needed varies, depending on the frequency and size of I/O writes to the primary volume and how long you need to keep the capacity.
- In general, choose a larger capacity for reserved capacity if one or both of these conditions exist:
  - You intend to keep the mirrored pair for a long period of time.
  - A large percentage of data blocks will change on the primary volume due to heavy I/O activity. Use historical performance data or other operating system utilities to help you determine typical I/O activity to the primary volume.
Select Finish to complete the asynchronous mirroring sequence.

Results

Unified Manager performs the following actions:

Begins initial synchronization between the local storage system and the remote storage system.
Creates the reserved capacity for the mirrored pair on the local storage system and on the remote storage system.

If the volume being mirrored is a thin volume, only the provisioned blocks (allocated capacity rather than reported capacity) are transferred to the secondary volume during the initial synchronization. This reduces the amount of data that must be transferred to complete the initial synchronization.