Veritas Access Appliance Administrator's Guide
- Section I. Introducing Access Appliance
- Section II. Configuring Access Appliance
- Managing users
- Configuring the network
- Configuring authentication services
- Configuring user authentication using digital certificates or smart cards
- Section III. Managing Access Appliance storage
- Configuring storage
- Managing disks
- Access Appliance as an iSCSI target
- Configuring storage
- Section IV. Managing Access Appliance file access services
- Configuring the NFS server
- Setting up Kerberos authentication for NFS clients
- Using Access Appliance as a CIFS server
- About configuring CIFS for Active Directory (AD) domain mode
- About setting trusted domains
- About managing home directories
- About CIFS clustering modes
- About migrating CIFS shares and home directories
- About managing local users and groups
- Using Access Appliance as an Object Store server
- Configuring the NFS server
- Section V. Managing Access Appliance security
- Section VI. Monitoring and troubleshooting
- Configuring event notifications and audit logs
- About alert management
- Appliance log files
- Configuring event notifications and audit logs
- Section VII. Provisioning and managing Access Appliance file systems
- Creating and maintaining file systems
- Considerations for creating a file system
- About managing application I/O workloads using maximum IOPS settings
- Modifying a file system
- Managing a file system
- Creating and maintaining file systems
- Section VIII. Provisioning and managing Access Appliance shares
- Creating shares for applications
- Creating and maintaining NFS shares
- About the NFS shares
- Creating and maintaining CIFS shares
- About the CIFS shares
- About managing CIFS shares for Enterprise Vault
- Integrating Access Appliance with Data Insight
- Section IX. Managing Access Appliance storage services
- Configuring episodic replication
- Episodic replication job failover and failback
- Configuring continuous replication
- How Access Appliance continuous replication works
- Continuous replication failover and failback
- Using snapshots
- Using instant rollbacks
- Configuring episodic replication
- Section X. Reference
How data flows in continuous replication synchronous mode
In synchronous mode of continuous replication, CVR processes an incoming write by performing the following steps.
CVR receives a write on the primary host.
CVR writes it to the primary SRL.
CVR sends the write to the secondary host and waits for the synchronous network acknowledgments from the secondary hosts. At the same time, CVR writes to the data volumes on the primary host.
On the secondary host, CVR receives the write, processes it, and sends a network acknowledgment to the primary host.
CVR sends writes to the data volumes on the secondary host. When the primary host receives a network acknowledgment from the secondary host, CVR acknowledges to the application that the write is complete.
Note:
The secondary RVG sends the network acknowledgment as soon as the write is received in the CVR kernel memory. This removes the time required to write to the secondary data volumes from the application latency. On the primary host, CVR does not wait for data to be written to the secondary data volumes. This improves application performance. However, CVR tracks all such acknowledged writes that have not been written to the data volumes. CVR can replay these tracked writes if the secondary host crashes before writing to the data volumes on the secondary host or if the primary host crashes before it receives the data acknowledgment.
When the write is written to the data volumes on the secondary host, CVR on the secondary host sends a data acknowledgment to the primary host. CVR marks the write as complete in the SRL when the primary receives the data acknowledgment from all the secondary hosts.
The bandwidth available for replication between primary and secondary sites should be able to handle the rate at which data is being written on the primary site. With synchronous continuous replication, the writes on file systems on primary site are completed after it is replicated to the secondary site. Hence, Veritas recommends that you have a high bandwidth for replication with synchronous continuous replication.