Saturday, December 31, 2011

Reiser and program development

Software development can be a slow process, but in many respects that is the best approach.  But this slow process should ideally be a series of small developments, each tested and reviewed on a continuous basis.

An example is the Reiser handler for CnW Recovery.  This was written in response to a an internal job to recover files from a failed HP Media Vault device.  The disks were OK, but the RAID had failed.  The development required was both support for JBOD (Job bunch of disks) and the complex Reiser format.  The job was done, and all data recovered.  ie Version 1 worked.

The next requirement came to read deleted files.  Deleted files on Reiser, according to many Internet sites is not possible, so CnW developed a method that works to about 80% success, a figure that varies and depends on many factors.

When software is released, there are often problems as unseen configurations, or failures crop up.  One by one these are fixed, and the product improves.  Currently, there is a good engine for HP Mediavault recovery, and many successful recoveries have been performed.

Along with a good engine, an easy to use interface has to be developed, and here the problems can expand. Users can be extremely computer literate, or beginners.  Most users are not experts in data recovery and so there are many terms and concepts unfamiliar to them.  A good place to start is with the Help system, but not many users think they need this.  There is also the expectation that because one can turn a computer on, one is an expert in all fields of computing, including data recovery.

One solution to this problem is to give no options, and only a single path through the software.  For predictable failures, and known configurations this can be implemented, and an example in CnW is the wizard for failed mini DVDs, to produce a new video disk.  For devices such as a HP RAID, there are several variations, and different requirements.  To this end, the chosen approach has been to try and trap errors, and give possible solutions.  At the same time, intelligence is built into the program to try and determine the original configuration, and point to a solution.

With HP Raid disks many users do not know if the disk is a mirrored disk, or a pair of disks.  Routines can be built into the program to indicate that the single disk is probably the second of a pair, or that an extra disk is likely to be required, and configured as a JBOD.

The overall result of this development is a program that will result in fewer calls for support, and a quicker solution for users who do not want to read the manual, but just get a solution.