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LiteSpeed for SQL Server 8.6 - Configure Log Shipping Guide

Test Optimal Backup Settings

Higher compression levels result in smaller backup files, but they also may consume additional CPU. If the server does not have sufficient CPU, then the backup may take longer to complete. The Backup Analyzer evaluates different settings, such as compression level, striping, and backup destinations, to help you determine optimal backup settings.

NOTE: When running the Backup Analyzer, follow these guidelines for the best results:
Minimum: 1 GB sample size.
Recommendation: 10 GB sample size. The combination of compression levels, encryption options, and backup locations should be considered. For example, if you sample 4 GB of data with 10 different tests, LiteSpeed will take the same amount of time as it takes to back up 40 GB. On very large databases, you can speed up the analysis by reducing the number of backup combinations or by reducing the amount of sample data.

Backup Analyzer Wizard

The Backup Analyzer wizard guides you through selecting the backup parameters to test. The wizard tests all of the different combinations of your selected parameters by backing up a portion of the database. It does not interfere with existing backup schedules or sets.

To run the Backup Analyzer wizard

  1. Select the Backup Manager pane (CTRL+1).

  2. Right-click the database and select Backup Analyzer Wizard.


    • To test striped backups, click Add to add several destinations and select the Test backup striping to selected backup locations checkbox on the Backup Location page.
    • If you add more than two destinations, select both checkboxes to test all destination combinations.
    • If you select a large number of backup parameters, you may want to schedule the tests to run at a specified time within the LiteSpeed Analyzer job.
  3. Click Next.
  4. On the Backup Location screen, select Backup to (Disk, Cloud, or TSM Backup) and Backup locations. Add or remove backups from the locations. Additionally select striping options.
  5. Click Next.
  6. On the Data Sample screen, enter the amount of data to sample in megabytes or the percentage of data to test.
  7. Click Next.
  8. On the Compression Level screen, select the compression levels to test. Any combination of compression levels from 0 to 8 are available. You can also specify additional backup advanced options.

    Review the following additional information about the advanced options:

    Compression threads

    Determines the number of threads used for the backup. You will achieve the best results by specifying multiple threads, but the exact value depends on several factors including: processors available, affinity setting, compression level, encryption settings, IO device speed, and SQL Server responsiveness. The default is n-1 threads, where n is the number of processors.

    Max transfer size

    Enter the maximum backup file size in bytes. . The possible values are multiples of 65536 bytes (64 KB) ranging up to 4,194,304 bytes (4 MB). The default is 1048576.

    Buffer count

    Enter the number of SQL Server buffers available for a LiteSpeed operation. The default is set by SQL Server.

    CPU throttle

    Enter the maximum percentage of CPU that LiteSpeed can use for the process. The default is 100.

    Processor affinity

    Click to select which processors LiteSpeed can use. The default is 0, which allows LiteSpeed to use all available system processors.

    Processor priority

    Select the priority of the backup over other transactions or processes running on the same server. The default is Normal.

    Network resilience

    If LiteSpeed fails to write disk backups or reads from disk, it waits and retries the operation. You can enable and disable and control the number of times to retry and the amount of time to wait before retrying.

    • Number of times to retry any given read/write attempt—The default is 4 retries. The maximum allowed setting is 1000 retries.
    • Wait period before each retry attempt (in seconds)—The default period to wait before retry is 15 seconds The maximum allowed setting is 300 seconds.

    For more information, see Network Resilience.

    TIP: Before you start tuning the CPU Throttle or Affinity parameters to adjust backup performance, try limiting the number of threads. If you decide to use an affinity value other than default, it is recommended that you limit the threading as well.

    NOTE: LiteSpeed defaults typically result in the best performance. You should only modify advanced options after careful planning and testing. For more information, see Configure LiteSpeed Defaults.

  1. Click Next.
  2. On the Execute Script screen, the list of databases to test is displayed.
  3. Click Next. The Backup Analyzer Wizard test scrip runs and displays the test results summary.
  4. Complete the wizard.

NOTE: After the required number of bytes is received for analysis, the process is intentionally aborted. This generates the VDI error messages in the LiteSpeed log files and the SQL Server error log. Please ignore them. ClosedClick here to see the examples of the error messages.

  • BackupMedium::ReportIoError: write failure on backup device 'VDI_B0F1C91D-201F-48DD-9D4B-5B16A1445D53_0'. Operating system error 995(The I/O operation has been aborted because of either a thread exit or an application request.).
  • BackupVirtualDeviceFile::RequestDurableMedia: Flush failure on backup device 'VDI_B0F1C91D-201F-48DD-9D4B-5B16A1445D53_1'.
  • BackupVirtualDeviceFile::ClearError: failure on backup device 'VDI_B4677313-6D48-4BC0-AC74-B3D0976E6077_1'.
  • SQLVDI: Loc=TriggerAbort. Desc=invoked. ErrorCode=(0).
  • SQLVDI: Loc=SignalAbort. Desc=Client initiates abort. ErrorCode=(0).

Scheduling Backup Analyzer

You can schedule analyzing from within the Backup Analyzer Wizard. An SQL Server job with the name "LiteSpeed Analyzer SERVERNAME.DATABASENAME" is created. View the list of Backup Analyzer jobs directly from the Backup Analyzer tab by clicking "Show Analyzer Jobs." Right-click on the job. You can change schedule, start/stop, disable or even delete the job. To view the script, select the "View in Job Manager" option and open the job properties from the Job Manager module. You can then go to the job step details.

Backup Analyzer Tab

The Backup Analyzer tab consists of the toolbar, graph, and grid. The Backup Analyzer toolbar is used to select the following items:

  • Existing test - View the existing test or use the drop down to select other tests.
  • Purge All - Click to remove all Backup Analyzer tests for the database.
  • Show Analyzer Jobs - Click to view all Backup Analyzer jobs.
  • New Test - Click to run the Backup Analyzer Wizard and begin a new test.
  • - Click to export the grid to Microsoft Excel.
  • - Click to print the grid.

The Backup Analyzer tab presents the test results in a graph and grid format:

  • Graph—Displays the backup duration and compression amount for each test in a bar graph so you can easily compare the results between size and duration. If you hover the mouse over the bar graph, test number, size, and duration are displayed. If you select a test in the grid, LiteSpeed indicates the corresponding test in the bar graph with a yellow border around it. You can view previous tests by changing the Existing test field. 

  • Grid—Displays the details of each test in columnar format. LiteSpeed indicates its recommendation with the number indicated first in the Test Number column and a yellow box around the test bar graph. Review the following for additional information:

    Tip: .Use the Grid horizontal scroll bar to view other table columns.

    Column Description
    Test Number

    The number assigned by the Backup Analyzer.


    The compression level that is used for a particular database backup test.


    Indicates enabled encryption for the database backup.

    Estimated Duration

    The approximate time allotted to run the database backup.

    Estimated Backup Size (MB)

    The approximate size of the backed up database.

    Database Size (MB)

    The amount of disk space the database occupies.

    Compression (MB)

    The amount of disk space you can save with this compression ratio.

    Compression (%)

    Data compression ratio.

    Read Speed (MB/Sec) Maximum read speed.
    Throughput (MB/Sec) Actual speed of processing data (compression and encryption).
    Backup Speed (MB/Sec) Virtual write speed of the backup. Compare this value to Throughput and Read Speed to determine if you are experiencing a write-bound issue.
    Write Speed (MB/Sec) Actual write speed. It shows how quickly the compressed data stream is written to the destination disk.
    Stripes Number of stripes associated with the backup.
    Destination Backup destination directory location.
    Threads Number of threads associated with the backup.

    You can double-click a row for more information about the test.

    Tip: For panes that have grids, you can sort, group, move, and remove the columns:

    • To sort and group the records, right-click a column header and select the appropriate options.
    • To sort records against multiple columns, click column headers while holding the SHIFT key. For example, to sort by type and then by name, click the Type column header and then SHIFT+click the Name column header.
    • To add or remove columns, right-click a column header and select Column Chooser. Add a column by dragging it from the list into the column headers. Remove a column by dragging its column header into the list.
    • To move a column, drag the column header to the new location.


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