End users, network and system administrators are becoming acutely aware that their current backup software solutions are failing at the very thing they were purchased to do; backing up the most critical data in their organisation.
The reason for this backup failure is that the most important files created, files changing regularly and in use by business-critical applications performing important functions on this data cannot be interrupted, as operational requirements now often call for 24/7 uptime, applications often accessing related files spread across multiple volumes, making point in time backups difficult or unfeasible using traditional approaches. If files are open or in use, e.g., e-mails, databases, Customer Relationship Management (CRM), and accounting for business-critical server applications such as Microsoft Exchange Server and Microsoft SQL Server that run continuously, a backup program cannot gain access to the file's contents. Historically, server applications were run during regular business hours only and so backups (also referred to as a cold backup) were carried out in the early hours when the applications could be stopped or offline without causing problems. Even if a backup program can access an open file, it still runs the risk of creating an inconsistent backup. Open file backups (also referred to as hot or dynamic backups) can be a major limitation of many business-critical applications that are typically performing functions. It is also problematic for desktop and notebook computers too.
For this reason most backup programs skip open files altogether.
The amount of data needing to be backed up has grown geometrically, as has the data lost; operational hours have increased, and the backup window is ever decreasing to accomplish the backup.
Specifically, any of three consequences can occur and none of them are desirable:
- Files are skipped: some backup packages will come back later and retry open files, however most application data will still be open, and therefore these files will be skipped again. The problem here is that only important applications run while a backup executes, which implies that the important data will not be backed up.
- Users are locked out of their applications: the backup application will lock the files while the backup is taking place. Users then receive a “” error.
- The backup is forced: in this instance, if any changes occur to a file during the backup, only part of the changes might get captured by the backup software, while other changes may be in areas of the file that have already been read for backup. Hence, the data on tape will be corrupt. This is a very serious scenario, since the administrator assumes there is a restorable copy of the file on tape, when in fact that data is unusable.
To overcome the open file, in use file, conundrum one approach is to implement copy-on-write for the benefit of backup applications. When a backup application opens a file, other applications are still allowed to write to the file. To avoid mixing old and new data in the backup application, the data being overwritten is copied to a side store. If regular applications request this data, the read is handled by the regular Windows file system drivers. When a backup application requests this data, the data is retrieved from the side store.
Genie-soft have developed their own online backup program, that complements their backup program family, called File Access Manager (FAM) - a Windows XP and Windows Server 2003 shadow-copy aware application that can receive freeze and thaw notifications to ensure that backup copies of data files are internally consistent.
FAM monitors the filesystem for read requests coming from backup programs. FAM recognises backup family of programs that run on the same system as well as those running on remote systems. When the backup operation is initiated, FAM determines a point in time when there are no partial transactions pending on the system. Once it discovers this state, FAM begins maintaining a dynamically allocated pre-write cache for each open file on the system. Meanwhile, users of the data have normal read and write access to their files, and the information on disk is what would be expected without a backup running. The value FAM brings is its ability to allow backup programs to deal with open files concurrently.
With FAM (integrated into GBM Server) business operations can continue uninterrupted yet all critical data will be protected against loss. Related files spread across multiple volumes are captured simultaneously, ensuring that the complex associations between files remain intact following a restore.
See: Backup (Why Should I?), Data, Data Loss and Data Recovery, and Volume Shadow Copy.
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