Summary
This article describes how to estimate the Block Level Incremental (BLI) change rate on a Windows 2003 Server.
Resolution
Introduction
Catalogic Software Backup Express supports block level backup technology for backing up data to both disk and tape. Unlike file level change rates, block level change rates are much more difficult to measure accurately. This document introduces a method (currently only supported on servers running the Windows 2003 32-bit operating system) to create change journal block level maps which can be used to calculate the BLI change rate. In order to do this, a Catalogic Software developed utility needs to be installed on the server first. Please contact Catalogic Software to download this utility. This utility (called SnapMgr) will function on servers with or without Backup Express installed.
Installing and Configuring SnapMgr
Download and extract the file bexsnapmgr.zip into the folder c:\bex on the server in question (this assumes that Backup Express is not installed in c:\bex. If that is the case, extract bexsnapmgr.zip into a different folder. Do not extract this file into the current Backup Express installation folder if Backup Express is installed on the server). Then execute the file c:\bex\tools\bexsnapmgr.bat, which in turn will start the java application. If Backup Express is not installed on this server, the snapshot driver needs to be installed first before BLI changes can be measured. This is done by selecting the Driver Update tab, and then the StBernardEOFMDriver from the pull-down menu. Click on install (shown below) to install the driver (Note:do this only if Backup Express is not installed on the server):
After a successful install, the user will be prompted to reboot the server which will load the snapshot driver. Verify that this driver loaded successfully by examining the Windows System Event log after the reboot. If the driver loaded successfully, and entry with Source: OFMLvDrv will be listed. This concludes the installation of SnapMgr.
Measuring Block Level Incremental Changes
In order to measure BLI changes, one will again execute the utility c:\bex\tools\bexsnapmgr.bex and select the tab SnapVaultBackupSimulation (as shown below):
Select All Application Components from the first pull-down, and Node (or the drive letter that needs to be analyzed for BLI changes). In most cases the entire node should be selected. Then simulate the BLI backup by clicking on Backup. This process can take a few minutes, and updates will be provided in the DOS window from which the .bat file was initially executed. A pop-up window will display the information at the conclusion of the backup simulation. This process simulates a BLI backup - no actual data is backed up. An example pop-up window is displayed below:
This shows that for the logical volume C: a total of 3,789,103,104 bytes will be backed up. This is the initial (Base) backup job. By running the backup simulation again, the BLI values (block-level incremental changes) since this previous backup will be displayed:
This shows that the BLI backup will only backup 298,209,280 bytes of data. This simulation should now be run periodically to simulate BLI (OSSV or Express Image) backups. The application (SnapMgr) does not need to be up all the time between simulations. Simply restart the application when a backup simulation should be run. All the information regarding the backup simulations is logged in .smg files in the logs folder, so no need to note all the information from the pop-up windows (shown above). At the conclusion of the test, please email all these files in c:\bex\logs as well as the X:\Backup Express Change Journal\*.bex files (X=C, D, E, etc.) to Catalogic Software for analysis.
Note: The Backup Express Change Journal folder is hidden by default, so make sure to uncheck the following three option in Windows Explorer: Tools|FolderOption|View|HideProtectedOperatingSystemFiles(Recommended), Tools|FolderOption|View|ShowHidenFilesAndFolders and Tools|FolderOptions|View|HideOperatiingSystemFiles first.
File Analysis
The Backup Express Change Journal folder (X:\Backup Express Change Journal) contains files with extensions .bex that lists all the blocks that has changed since the previous BLI backup. The following screenshot shows an example of the contents of the Backup Express Change Journal folder:
In this example the backup simulation was ran a total of five times (once for the base (initial) backup and four BLI backups). The .bex file corresponding to the base backup will always have as part of the file name a 0.0.bex. Each subsequent run will create a corresponding .bex file that lists the blocks that has changed since the previous BLI run. In our example, the file named (last one in the list)
{d8dcf779}.1147710606.1147710300.bex
contains a listing of the blocks that has changed since the backup that ran on 5/15/06 at 12:25 PM (the timestamp of the previous .bex file). These files are written in binary format and can be analyzed by using the SnapMgr utility so:
In this example, all the .bex files from the Backup Express Change Journal folder was copied into c:\c_drive and the file {d8dcf779}.1147710606.1147710300.bex was analyzed. The block size (4096 bytes) should be entered as well. By clicking Query, the BLI change size (in bytes) will be displayed for this file:
This shows that 57,221,120 bytes (roughly 54.5 MB) has changed for this drive (C in our example) between 12:25PM and 12:30PM.
Another way of obtaining this information is to analyze the .smg files that are created when the backup simulation runs. Looking at the .smg file that got created for the 12:30PM (last) BLI job, the entry:
GETTOTDATA [\\?\Volume{f8f442af-4e49-11da-9e08-806e6f6e6963}\\Backup Express Change Journal\{d8dcf779}.1147710606.1147710300.bex] BLOCK[4096] DATA[57221120]
shows the blocksize of 4096 and the bytes changed (57221120). This log also reports on the size of the C: drive (in this example)
Mon May 15 12:17:37 2006 SNB 3066D 3932: FreeSize [1859850240]
Mon May 15 12:17:37 2006 SNB 3066D 3932: TotalSize [5362847744]
from which the allocated size (total - free) is 3,502,997,504 bytes, and %BLI change can be calculated as (57,221,120/3,502,997,504 * 100%) = 1.6%.
Cleanup
At the conclusion of the BLI analysis, unload the snapshot driver by using the SnapMgr tool as shown below (Note: do this only for the case where Backup Express was not installed on the server):
This requires a reboot of the server. After the reboot, remove the c:\bex as well as the X:\Backup Express Change Journal folders.