Data replication between the and 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 operation to copy the modified data blocks to the secondary virtual disk at the secondary .
The type of chosen when creating the determines when the I/O completion indication is sent to the host application,
signaling that the data has successfully been copied to the secondary storage array.
Choose one of the write modes shown in the following table.
Synchronous (recommended)
This write mode offers the best chance of full data recovery from the secondary storage array in the event of a disaster, at the expense of host I/O performance.
When this write mode is selected, any host write requests
are written to the primary virtual disk and then copied to the secondary storage virtual disk. The RAID controller module sends an I/O completion indication to the host system after the copy has been successfully completed.
This write mode is selected by default and is the recommended write mode.
Asynchronous
This write mode offers faster host I/O performance, but does not guarantee that the copy has been successfully completed before processing the next write request.
When this write mode is selected, host write requests are written to the primary virtual disk, and the RAID controller module sends an I/O completion indication back to the host system before the data has been successfully copied to the secondary storage array.