Dell POWERVAULT MD3600F - Manual (Page 195)

Configuration: Premium Feature— Remote Replication 195
Selecting the Secondary Virtual Disk
CAUTION: Creating a replicated virtual disk pair starts a process between the
primary and secondary virtual disks that overwrites all existing data on the
secondary virtual disk and set the disk to read-only access. If you have existing
data on your secondary virtual disk stop all I/O to the disk, back up the data, and
unmount any file systems mounted to the secondary virtual disk before creating
the replicated virtual disk pair.
1 Select the remote storage array and the primary virtual disk.
2 In the Select Secondary Virtual Disk (Create Remote Replication)
wizard, select the secondary virtual disk.
NOTE: The secondary virtual disk must have a capacity equal to or greater
than the capacity of the primary virtual disk.
3 Click Next.
The Set Write Mode (Create Remote Replication) wizard is displayed.
Go to "Setting the Write Mode" on page 195.
Setting the Write Mode
The secondary host ports on the storage arrays are reserved for data
synchronization between the primary virtual disk and the secondary virtual
disk in a replicated virtual disk pair. You can set remote replication to write
either synchronously or asynchronously.
• In the synchronous mode, the RAID controller module on the primary
virtual disk sends an I/O completion message back to the host storage array
after the data is successfully copied to the secondary storage array. The
synchronous mode is the preferred mode of operation, since it offers the
best chance of full data recovery from the secondary storage array in the
event of a disaster. However, a synchronous replication mode can degrade
the I/O performance of the host when long-distance data transfer is
involved.
• In the asynchronous mode, the RAID controller module on the primary
storage array sends an I/O completion message to the host storage array
before the data is successfully copied to the secondary storage array. The
asynchronous mode offers faster host I/O performance; however, it does
not guarantee that data was successfully written to the secondary virtual
disk or that the write requests were completed on the secondary virtual
disk in the same order they were initiated. In asynchronous mode, you can
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