Recovering Deleted/Lost/Missing Data From Novell Servers
- Journaling -> This significantly reduces the number of errors that happen when an operation is interrupted unexpectedly (resulting from occurrences such as a power failure or system failure).
- File Snapshot -> This feature allows transient copies of open files to be made. Taking advantage of this, backups of even open files are possible. This feature can be activated using the console command:
nss /FileCopyOnWrite=(Volume Name) OR nss /FileCopyOnWrite=all
For a complete description of this feature, visit:
http://www.novell.com/documentation/nw65/index.html?page=/documentation/nw65/nss_enu/data/ajhv67e.html
- Pool Snapshot -> This feature allows you to take a snapshot of a data pool as it exists, including open files. This can be helpful for backup, maintenance, and restoration of lost data.
A snapshot can be taken using the console command:
mm snap create (snappool)(datapool)(snapname)
A previously taken snapshot can be activated using the console command:
mm snap activate (snapname)
A more extensive list of Pool Snapshot capabilities is given at:
http://www.novell.com/documentation/nw65/index.html?page=/documentation/nw65/nss_enu/data/br18vpz.html
Even though these features offer data safety up to a certain level, the one big limitation for these features above is that all backups are metadata-based only. This means that a data disaster on a big scale, with a files actual core data getting lost/deleted, cannot be resolved using these features. What is needed in such a scenario is a complete scan of the disk surface to look for deleted/missing entries. This can only be done by advanced data recovery software and is a must-use when the above methods fail.
2. Setting up the hardware (for a recovery process)
2.1 Basic Do's and Don'ts
When data is seemingly 'deleted' from a disk, the actual data is not removed. Only the reference information of the file is modified so that the space that a file occupies on the disk is marked as 'free-space' and is made available for writing on. But until that space is actually overwritten by other data, the original data remains intact and is therefore recoverable.
Since 'lost' data being overwritten is a major concern, it is imperative that the volume containing lost data is not used at all. Even leaving the server on, without any activity, causes many tiny files to be written/updated every few seconds. This increases the chance of lost data being overwritten and reduces the possibility of total data recovery. Therefore, after any instance of data loss – be it a single deleted file or a total disk failure – it is preferable to disconnect the affected server disk.
Following episodes of data loss:
 Do's
- Turn off the machine immediately
- Disconnect the server disk
 Don'ts
- Never restart the machine in the hope that this will solve the problem – a restart involves many files being generated which may result in overwriting of lost data which will in turn reduce the possibility of total data recovery
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