Which resynchronization method should I choose?

Data replication between the  and  in a  is managed by the  and is transparent to  machines and applications. When the  of the primary virtual disk receives a write request from a host, the RAID controller module first logs information about the write to a , and then writes the data to the primary virtual disk. The RAID controller module then initiates a write operation to copy the affected data to the secondary virtual disk on the remote, secondary .

If a link interruption or  error prevents communication with the secondary storage array, the RAID controller module owner of the primary virtual disk transitions the mirrored pair into an  status and sends an I/O completion to host sending the write request. The host can continue to issue write requests to the primary virtual disk, but  to the secondary virtual disk do not take place.

When connectivity is restored between the RAID controller module owner of the primary virtual disk and the RAID controller module owner of the secondary virtual disk,  takes place. Only the blocks of data that have changed on the primary virtual disk during the link interruption are copied to the secondary virtual disk.

Two resynchronization methods are available in the current release of storage management software, as shown in the following table.

Resynchronization method Description

 (recommended method)

When enabled, resynchronization of the data on the primary virtual disk and secondary virtual disk can be started manually after communication has been restored to the Unsynchronized mirrored pair.

Note: Only the blocks of data that have changed on the primary virtual disk during the link interruption are copied to the secondary virtual disk.

The Manual Resynchronization option is the recommended method because it allows you to manage the resynchronization process in a way that provides best opportunity for recovering data.

When this option is selected and a communication failure occurs between the primary and secondary virtual disks, the Remote Virtual Disk Mirror transitions to an Unsynchronized state. Any write requests to the primary virtual disk are logged and a Needs Attention status is displayed for the storage array.

After the RAID controller module owner of the primary virtual disk detects that communication has been restored, the Remote Virtual Disk Mirror remains in an Unsychronized state until you select Virtual Disk >> Remote Virtual Disk Mirroring >> Resume.

Important: Any communication disruptions between the primary and secondary storage arrays while resynchronization is underway could result in a mix of new and old data on the secondary virtual disk. This situation renders the data unusable in a disaster recovery situation.

When enabled, automatic resynchronization starts immediately after the RAID controller module detects that communication is restored for an Unsynchronized mirrored pair.

Note: Only the blocks of data that have changed on the primary virtual disk during the link interruption are copied to the secondary virtual disk.

When the Automatic Resynchronization option is selected and a communication failure occurs between the primary and secondary storage arrays, the RAID controller module owner of the primary virtual disk starts resynchronizing the primary and secondary virtual disks immediately after detecting that communication has been restored.