A configuration option for , which determines when an I/O completion indication is sent to the application to signal that data has successfully been copied from the primary to the secondary storage array.
There are currently type write modes available:
Synchronous:
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 will be written to the and then copied to the secondary storage virtual disk. The 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 preferred write mode.
Asynchronous:
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 then 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.