To set up SyncMirror with array LUNs, you must fulfill standard requirements for any SyncMirror deployment, plus a number of requirements that are unique to setting up SyncMirror with array LUNs. There are a few additional requirements specific to setting up SyncMirror for a MetroCluster configuration with array LUNs.
When planning for mirroring of aggregates for systems that can use both array LUNs and disks, consider the following:
You cannot mirror an aggregate between a native disk shelf on a Data ONTAP system and a storage array.
The rules for setting up mirroring with disks are the same for FAS systems and V-Series systems.
SyncMirror requires twice as many array LUNs as you ordinarily would need for storage so you can create mirrored aggregates. The same number and size of array LUNs must be available in each set of array LUNs that you are going to use for the two plexes of the aggregate.
For example, assume that you have a 40-GB aggregate that is composed of four 10-GB LUNs, and you want to mirror it. You must have four 10-GB LUNs available in the local location and four 10-GB LUNs in the remote location to be able to mirror the aggregate.
If the LUNs are not the same size, the following occurs:
However, space is wasted and cannot be reused. For example, if the array LUN in pool0 is 10 GB and the array LUN in pool0 is 20 GB, the mirror will be 10 GB (the pool0 LUN size.) The remaining 10 GB of space in the pool0 LUN is wasted and cannot be reused.
For example, if the pool0 (local) array LUN is 20 GB and the pool0 array LUN is 10 GB, mirroring fails.
For a MetroCluster configuration that uses array LUNs, you must use two separate storage arrays for the mirror. For SyncMirror that is not used in a MetroCluster configuration with array LUNs, you can use one or two storage arrays.
If you are using two storage arrays for mirroring, the requirements are as follows:
If you are using only one storage array for mirroring, the requirements are as follows:
You must assign all array LUNs that are used for the plexes of the aggregate to the same Data ONTAP system. This system owns the aggregate.
All array LUNs in both sets of LUNs that are used for the plexes of the aggregate must be the same checksum type.
You want the data mirrored exactly on the two storage arrays so that if one plex becomes unavailable, all data can continue to be served. How you assign array LUNs to SyncMirror pools determines how the array LUNs are distributed between the two storage arrays in the MetroCluster configuration.
For array LUNs, you must explicitly assign each array LUN to the local pool or the remote pool. To group the LUNs correctly, you must plan ahead so that you know which array LUNs are located on which storage array. Data ONTAP cannot determine this for you.
A MetroCluster configuration can preserve data only if volumes are mirrored. Unmirrored aggregates are not supported.
In addition, you must configure each plex to be on a separate set of array LUNs on different storage arrays.
For more information about a MetroCluster configuration that uses array LUNs, see the Clustered Data ONTAP 8.3 MetroCluster Installation and Configuration Guide.
Before you create your aggregate and mirror it, you must ensure that there are two paths to an array LUN for a given Data ONTAP system.
For more information about checking paths to array LUNs, see the FlexArray Virtualization Installation Requirements and Reference Guide.