| Introduction | | | | flash the data to the disk and freeze IO writes from |
| Many Microsoft Window applications (like Exchange, | | | | the application during the time the VSS takes the |
| MS-SQL, etc) are critical to the daily core functionality | | | | snapshots (usually few seconds). This ensures |
| for many companies and organizations. Managing the | | | | application data consistency when recovery is |
| data backup for these applications presents new | | | | needed. If there is no VSS writer then VSS will go |
| challenges for system administrators. While there is | | | | directly to the next step but there is no guarantee |
| an ever increasing need for more and more data to | | | | that the data is in a consistent state. |
| be backed up, at the same time the system | | | | STEP 3. Path 3: VSS requests a provider to create a |
| administrator must cope with the issue of shrinking | | | | snapshot. There are three kinds of VSS providers: |
| backup windows in which the application can be | | | | Hardware, Software and System. A system provider |
| taken offline in order to backup the application data. | | | | is part of the Windows 2003 OS and it will take |
| Another issue to contend with is the performance hit | | | | snapshots and keep them but only at the OS level. A |
| the production server takes when backup is running. | | | | hardware provider is usually a storage provider, like |
| Microsoft Volume Shadow Copy Service (VSS) and | | | | SANRAD Iscsi V-Switch, which creates and maintains |
| SANRAD iSCSI V-Switch acting as VSS storage | | | | snapshots at the storage hardware level. VSS |
| provider can help the system administrator resolve | | | | chooses the provider from a list (first on the list with |
| these issues by: | | | | priority given to hardware provider if one exists). |
| - Eliminating the need to take the application offline. | | | | STEP 4. Path 4: VSS goes back to the VSS Writer (if |
| - Quickly responding to the increasing need for | | | | it exists) and allows it to unfreeze the application I/O |
| storage. | | | | activity and resume normal activity. |
| - Enabling fast backup and restore by backing up to | | | | STEP 5. Path 5: VSS goes back to the requestor |
| disks and offloading the backup performance hit from | | | | (backup application) and gives it the location of the |
| the production volumes and servers. | | | | snapshots so it can start the backup from the |
| This application note describes VSS, how it works, | | | | snapshots. |
| the required basic configuration in order for VSS to | | | | STEP 6. Path 6: Once backup is complete, the |
| work with the SANRAD V-Switch to create | | | | requestor informs VSS which in turn informs the VSS |
| snapshots as well as the backup design options using | | | | provider to delete the snapshots. |
| VSS and SANRAD V-Switch. We use Veritas' | | | | Summary |
| BackupExec (V10.0) to help us demonstrate taking | | | | The combined solution of Microsoft Volume Shadow |
| backups with VSS using SANRAD V-Switch. | | | | Copy Service (VSS), SANRAD V-Switch as the VSS |
| This application note assumes that the user has basic | | | | storage provider and backup VSS aware applications |
| knowledge of how to use SANRAD V-Switch to | | | | (like Veritas BackupExec V10) allow companies to |
| configure volumes and expose them to the servers | | | | offload backup jobs from the production |
| as disks. The user should also be familiar with | | | | environment, leave applications up for user access |
| Microsoft Iscsi initiator for connecting Windows 2003 | | | | while backing up the data and have a data life cycle |
| server to the exposed iSCSI volumes by the | | | | for regulations compliance. |
| SANRAD V-Switch. | | | | This article describes VSS, how it works, the required |
| What is VSS? | | | | basic configuration in order for VSS to work with the |
| Microsoft Volume Shadow Copy Service (VSS) | | | | SANRAD V-Switch to create snapshots as well as |
| provides the backup infrastructure for the Windows | | | | the backup design options using VSS and SANRAD |
| Server 2003 operating systems, as well as a | | | | V-Switch. We use Veritas' BackupExec (V10.0) to |
| mechanism for creating consistent point-in-time copies | | | | help us demonstrate taking backups with VSS using |
| of data known as shadow copies or snapshots. | | | | SANRAD V-Switch. |
| VSS can produce consistent snapshots by | | | | It further discusses about Configuring Windows |
| coordinating between different applications (business, | | | | Application server to use the V-Switch as the VSS |
| file-system services, backup) and storage hardware. | | | | Hardware Provider, Configuring the V-Switch for |
| The following steps describe VSS Architecture: | | | | VSS, Configuring the Backup Application to use VSS |
| STEP 1. Path 1: The Requestor (usually a backup | | | | for the backup job, |
| application) make a request to VSS (running on the | | | | Backup design options using the V-Switch as the VSS |
| application server) to create snapshots of production | | | | hardware provider, D2D - Offload the backup from |
| volumes so that backups can be made from the | | | | the production volumes, D2D - Offload the backup |
| snapshots and not from the production volumes. | | | | from production servers, |
| STEP 2. Path 2: If the volumes "belong" to an | | | | D2D - Save the backups in remote location with |
| application that has a VSS Writer (VSS aware | | | | SANRAD data replication, and D2D2T - Offload old |
| application like Exchange), the VSS requests the | | | | backups from disks to tape with SANRAD data |
| Writer to prepare the volumes. The Writer will usually | | | | replication. |