Recovering Deleted/Lost/Missing Data From Novell Servers

NSS v/s NWFS with respect to Data Safety and Protection

NSS is far superior to NWFS when it comes to data safety and protection

	NSS	NWFS
Error Correction	Presence of journal simplifies error correction/recovery	Entire volume must be scanned (VREPAIR) to determine errors
File Snapshot	Backup of open files	No such support available
Pool Snapshot	Backup of block in current state	No such support available
RAID Support	Supports RAID 0,1,5,10,15	Supports RAID 0,1,10
Data Shredding (Data Erasure)	Permanent data removal (overwriting over 7 passes)	No such support available

Data storage in Novell servers can be optimized using configurations such as Compressed Volumes, Sub-allocated Volumes, and Segmented Volumes. Data recovery software usually recovers data in its raw form, as they appear on the disk, disregarding any of the above configurations they may be in. Thus, the recovery of such data back to its original form presents a problem. Before we look at how such configurations can be retained even after recovery, let us first understand how data is arranged in such volumes.

Compressed Volumes

Data Compression refers to the process of storing data in a format that requires less space than usual. Compressing data is the same as packing data – reducing the amount of electronic 'space' data takes up, and compressed data usually consumes 2 to 4 times fewer bits. Typically, it is infrequently used data which is automatically compressed to save space.
Methods of compressing data include replacing multiple blank spaces with a character count, or replacing redundant data with shorter stand-in 'codes'.

Volumes can be compressed in NSS using the console command:

nss /Compression=(Volume Name) OR nss /Compression=all

Volume compression statistics can be viewed using the command:

CompScreen

Note: Volume compression is an irreversible process.

A listing of all Novell compression capabilities is available at: http://www.novell.com/documentation/nw65/index.html?page=/documentation/nw65/nss_enu/data/bpwtq9o.html

Sub-allocated Volumes

Sub-allocated volumes are a new feature and have been implemented in NetWare 4.x to overcome the problem of wasted disk space. These volumes are different from regular Novell volumes because they are more of a 'virtual' volume – one that is not 'visible', but exists nevertheless.

Sub-allocation refers to multiple file-endings sharing disk blocks. The data in a file is stored in the hard disk in multiple blocks, each block being a collection of sectors of standard size. There are, almost always, some unutilized sectors at the end of a file. These 'under-allocated' sectors of different files are combined together to form a separate 'virtual' volume.

For Example: Say, a volume stores data in blocks of 4 sectors, each sector having size = 512 bytes. Now, if there is a file containing 520 bytes of data, the first sector is entirely occupied and the remaining 8 bytes go into the second sector. This leaves 2 entire sectors unused. These unutilized sectors of different files are combined together to form a separate sub-allocated volume, thus saving space and optimizing data storage.