Since the introduction of Mac OS X Lion 10.7 every Mac user is willing to use it and most of them are about to, or have already upgraded. Most of the time the process is most likely to be completed properly, yet number of times one or the other problem occurs meanwhile and lead to abrupt termination or interruption in the process and other issues therein. This is why it is always asked & is really essential to acquire information in context of Lion compatibility. It is quite obvious and known to all, that the occurrence of data loss cannot be known, so all that remains within a users approach is keeping a backup of data at frequent intervals to cope up with data loss, if it occurs so. The same applies to OS X lion upgrade & data loss.

Some essential points to be complied with, when looking for upgrade to lion OS X -

• OS X lion is Intel based processor and thus the PowerPC based application which have been used till data would turn inaccessible leading to situation of data loss after upgrade, hence the compatibility need to be checked prior to installation. This can be done from apple icon → more info tab, where all PowerPC supported apps are shown and you can select its counterpart that would work on Mac
• Enough space minimum of 4 GB & upto 10 GB space should be available
• The OS should be one downloaded from the app store and do make sure that the snow leopard system used is version 10.6.8
• Most important of all, is the data you have and backing it is good idea before bringing any changes on to the system

What causes data loss after upgrade to Lion OS X 10.7?

The OS & the process are so designed, to enable it to be completed properly, yet different issues during upgrade to lion is not always evitable. The problem is most noticeably found to occur since, system's hard drive keep spinning on a continuous basis for operations to be performed, producing heat. Apart from the volume of data to be written to drive spinning required also increases as a result of bad blocks, if there exists any on the hard drive. This would therefore result in production of more heat, such immense increase may lead it to crash and this is the problem taking place during software and OS up-gradation.

So, if upgrade to lion 10.7 in your case does not end successfully due to system crash or your files are missing after that, the required fix is to be implemented and backup should thereafter be used for restoring lost files back. Other than those, in which backup is not available you could try for Mac recovery utilities for restore of missing, deleted and lost Mac files.