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Open File Manager

by Chris Taylor

If you are responsible for data recovery on a computer system, don't skip this article. It just might save your bacon! 

Did you know that your backups may be worthless? It surprised me to discover this fact. If you are running a 24x7 operation, you have to run your backups while people are using the system. This can put your data at risk. The problem stems from files that are open when the backup is run. 

There are three ways backup programs typically handle open files:

  • First, they simply skip the open file. NTBackup (the program that ships with NT) will dutifully add an entry to the log file (You do read the log files, right?) saying that it encountered an open file and skipped it.
  • They may force a write to tape. Most third party backup software can do this and lull you into thinking your data is OK.
  • Use a special purpose extension that handles a particular data type (for example, Exchange Server and SQL Server) to backup the data.

If you skip open files, providing you review your logs, at least you know what you are missing. In many cases, you can take steps to ensure a valid backup of the files. For example, at my office we have users' personal address books on a LAN drive. NTBackup will not backup these files if the person neglected to close Exchange before going home or if someone logged on from home while the backup is running. One solution: force everyone off the network while the backup runs. However, try to convince a couple of thousand users that the reason they can't use the network from midnight to 2:00 a.m. is for their own good! 

If you force a write to tape, much of the time, you will be OK. In the example above of personal address books, it will usually work well. Although the personal address books on our network are open these files do not experience a lot of write activity. There is a not-so-special case that it won't work. Consider a large database file with active transactions happening while the backup is running. If you force the backup program to backup that file, it will be backing up part of the file while other parts are undergoing rewrites. As the backup proceeds to later parts of the file, the earlier sections (already backed up to tape) may experience rewrites. In any case, your backup does not reflect the most current file data. If you ever have to restore this file, it may effectively be junk although you may not know it until it is too late. 

The third method, using a special extension to your backup software, is safe. These solutions are costly and typically very narrow in focus. You may need to purchase multiple extensions to handle all your file types or you may not find an extension for the file type you are using. 

I recommend that you investigate a fourth solution-Open File Manager (OFM) version 5.1 from St. Bernard Software. It eliminates the problems in an elegant and powerful manner. It allows you to backup safely any files and works with most backup programs: OFM currently supports 21 programs from 16 vendors. The concept is simple. When it finds an open file, it begins keeping track of changes to that file. Changes are written immediately to disk; your data is not at risk. While allowing the disk write to take place, it keeps track of the data that used to be there and puts it in a pre-write cache file. When the backup program tries to backup that portion of the file, OFM substitutes the data in the pre-write cache. You end up with a faithful copy of the file as it existed at the beginning of the backup operation. For cases requiring sets of files that must synchronize at a consistent stage, such as a database file and its indexes, OFM can handle the entire file system as a single entity. The entire file system backup will faithfully reproduce the data as it existed at the start of the backup. 

The pre-write cache can be configured to retain its contents until the backup software performs its verify phase. If disk space is limited, you can configure OFM to release the pre-write cache data as soon as each individual file is written. Other configuration options allow you to eliminate special handling of specific files or directories (such as the paging file or the TEMP directory) and to specify the location of the preview cache file. If you have multiple backup systems in your organization, you can manage OFM on all systems from a single console. 

A handy agent included with OFM allows you to configure an account to copy open files using the same technology. Numerous times I have tried the impossible: to access an open file on our network. OFM would have saved me running around getting users to close the file. This agent will act only over the network; users with a single, stand-alone machine can't benefit from this agent. 

OFM runs as a service under Windows NT 4 (Workstation or Server) or as an NLM under Novell Netware. The memory footprint under NT is around 1MB. 

I tested OFM on PUB II-the NT Workstation that runs our new BBS. The BBS software keeps about 50 files open (databases for messages, user accounts, indexes, etc.) whenever the BBS is running. OFM handled all these files perfectly and allowed NTBackup to perform a complete and accurate backup. 

OFM is definitely not for every situation. You must evaluate your own backup strategies; if they are adequate, do not spend more money. Perhaps you can modify your existing procedures to compensate for any deficiencies. Finally, you may decide to live with any data losses that occur. Please- if you choose this last course of action, consider carefully the risks to your company's bottom line and your own pay cheque. Don't tell your boss! 

OFM manager is not cheap. Single copies for NT Server are US$575.00. Quantity discounts are available; the smallest for NT Workstation is a 5-pack at US$495.00. 

St. Bernard Software currently has a promotion: any organization can request a free, full-function copy of the version for NT Workstation. I have requested a copy to use for OPCUG. St. Bernard is also offering a discount to OPCUG members. Contact Tod Helmink at 1-800-782-3762 and be certain to mention your club membership. A 15-day trial version is available from the company's website:

Bottom Line:

Open File Manager (Proprietary)
St. Bernard Software
US$575.00 (Single copy for NT Server)

Originally published: June, 1998

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