DataKeeper for Windows All Documentation - SIOS

Read and Write OperationsRead and Write OperationsAfter the volume mirror is created and the two drives on the primary and secondary servers are synchronized,the following events occur:• The system locks out all user access to the target volume; reads and writes are not allowed to thetarget volume. The source volume is accessible for both reads and writes.• Both mirrored and non-mirrored volume read operations arriving at the driver on the primary server arepassed on and allowed to complete normally without intervention. Reads of a mirrored volume on thesecondary system are not allowed, i.e., the secondary has not assumed the role of a failed primary.• Whenever the primary server receives a write request, the system first determines whether the requestis for a mirrored volume. If not, the write is allowed to complete normally without any furtherintervention. If the write request is for a mirrored volume, the request is handled depending on themirroring type:• If the type is synchronous, then the write request is sent to both the source and target volumesat the same time. Should an error occur during network transmission or while the target systemexecutes its write, the write process on the target is terminated. The source will then completeDataKeeper for Windows Technical DocumentationPage 17