Hardware installation for Synchronous Mirroringand Asynchronous MirroringThe Asynchronous Mirroring feature uses a remote point-in-time replication method. AsynchronousMirroring differs from Synchronous Mirroring in one essential way: it captures the state of the sourcevolume at a particular point in time and includes just the data that has changed since the last imagecapture. With Asynchronous Mirroring, the remote storage array is not fully synchronized with thelocal storage array, so if the operation needs to transition to the remote storage array due to a loss ofthe local storage array, some transactions could be lost.The Synchronous Mirroring feature is also used for online, real-time data replication between storagearrays over a remote distance. The storage array controllers manage the mirror operation. You createone or more mirrored pairs consisting of a primary volume at the local site and a secondary volume ata secondary, remote site. However, instead of batching the synchronization process using point-in-time snapshot images like in Asynchronous Mirroring, the primary volume copies all of the data fromthe primary volume to the secondary volume in a single operation. This full synchronization processtakes longer to complete, but creates a complete copy of the mirrored data. While this process is idealfor certain operations, make sure you fully understand both data mirror options before selecting oneover the other.See to the online help system for more information about the Synchronous Mirroring feature and theAsynchronous Mirroring feature, and for software-related procedures to set the configuration of thesefeatures and use them.Planning and site preparationThe Asynchronous Mirroring feature can be used with either Fibre Channel or iSCSI hostconnections. Asynchronous Mirroring requires a duplex controller configuration. The SynchronousMirroring feature can be used only with Fibre Channel connections. For Fibre Channel connections,youmust have Fibre Channel switches to create a fabric environment for data replication. For iSCSIconnections, switches are optional. The following restrictions apply to connections for AsynchronousMirroring or Synchronous Mirroring.• SAS and InfiniBand connections are not supported.• If an E5400 controller-drive tray has an InfiniBand HIC, it cannot have connections for mirroring.• iSCSI connections must use a host-connect port and not the management Ethernet port.With the Asynchronous Mirroring feature, the following considerations apply for combining FibreChannel and iSCSI connections:• If two storage arrays are connected through both Fibre Channel and iSCSI connections, only oneconnection type is used for a given asynchronous mirror group. However, if there are multipleasynchronous mirror groups, some asynchronous mirror groups can use Fibre Channelconnections while others use iSCSI connections.• Failover from a Fibre Channel connection to an iSCSI connection (or vice versa) is not supported.Switches require only minimal additional site preparation beyond basic storage array operation. Foradditional site preparation considerations for switches, including power requirements and physicaldimensions, refer to the documentation that is provided by the switch manufacturer.135
