Backup Mode

VSS-based backup utilizes the Microsoft SQL Server VSS Writer to obtain a consistent snapshot of the MS SQL databases, no spooling / staging of database file(s) is required during the backup process.

(Diagram from Microsoft)

• Fast and minimal interruption

  The database snapshot capture process is fast and can take place on a running server, as you may continue to work when the snapshot capturing is taking place, there may be another process that holds your input in some memory section until the snapshot capture is completed. That said, the whole snapshot capture is fast, so there is no need for you to stop working and it causes minimal interruption to your business operation.

• Significantly lesser disk burden

  VSS Snapshot typically requires much less additional disk space than clones which is the traditional backup method by spooling database into the temporary folder. Oftentimes, the capacity of the database to back up is huge and therefore the temporary folder would overload with the equal or even larger disk space if traditional backup method is used. By utilizing the VSS technology, it helps your system greatly reduce disk capacity burden and promote optimized performance.

• No Transaction Log Backup

  MS SQL does not support transaction log backup when VSS is used, therefore, transaction log backup will have to be done manually.

• Workaround is time consuming

  In order to truncate the transaction logs, you have to either change the Recovery model to Simple or perform a manual log truncation, which could be time consuming.

VSS based backup no longer requires backup of the transaction log files, however for databases configured in either full or bulk-logging recovery model, this may eventually result in transaction logs filling up the available disk space on the volume of the MS SQL Server.

A Guide for SQL Server Backup Application Vendors

To prevent this from occurring, it is recommended to change the recovery model of database selected for backup to simple recovery model.

Refer to the following steps for details:

1. In “SQL Server Management Studio”, expand Databases, select a user database, or expand System Databases and select a system database.
2. Right-click the corresponding database, then click Properties to open the "Database Properties" dialog box.
3. In the “Select a page” pane, click Options.
4. The current recovery model is displayed in the “Recovery model” list box. Modify the recovery model by selecting Simple from the model list.

By using the ODBC mode for MS SQL backup, database files are spooled to a temporary directory before they are uploaded to the backup destination.

• Support Automated Transaction Logs Backup

  Schedule backup of transaction log can be configured so that the transaction logs can be backed up periodically and the transaction logs are truncated automatically after each backup job.

• Support Point in Time Recovery

  The ability to restore to a point in time for all your transaction log backups.

• Support Backup of High Transaction Databases

  For databases which supports a high number of transactions which may require frequent backups. Transaction log backups at regular intervals are more suitable and less resource intensive than VSS based backups, i.e. transaction log backup every 60 minutes, 30 minutes, 15 minutes etc. depending on the database transaction volume.

• Large disk space required

  Since the database files will be spooled to a temporary folder before uploading to backup destination, investment on hard disk could be high if your MS SQL database size is large.

• Slower backup process

  By utilizing the conventional spooling method, it could take a long time to back up the database and the speed is subject to various factors, including database size, network transfer speed, backup frequency, etc.