I'm not a DX guy but I asked one - see below starting with: =>
Question 1 : If the Centera is configured for retention, which it is and it is using Goverenance SW, and DX policies are set for retention, If a user fetches after a purge or even before a move from the extended drive, the user will be required to save the file under a different file name correct?
=> If a file is under retention it can be fetched or purged, however can not be saved with the same name, it would have to be saved as a new file.
If that statement is true, then the backup/restore question is easily answered, in that with a new file, a restore will use the EA that DX creates to be able to restore the files as they will be two different files.
Question 2: Even though Centera is configured for retention, if a value of 0 is set for a DX retention value then it is said to not have any retention of files which can then lead to the ability to delete files. Aside from DX Recycle Bin, the only way to recover a deleted file at that time would be to recover from a piece of backup media.
=> This is correct. (This is also documented in all the Admin Guides under Centera section and DiskXtender)
If, however, the scenario is as above in question 1, if a file is fetched and changed then purged again, what happens to the EA,and C-Clip information of the file before it was changed? Is it altered to reflect two files now or just one file that was the original + changes?
=> 1. if file1.txt is under retention it can not be edited (it can be fetched and purged fine)
=> 2. File1.txt would be saved as file2.txt which is a new file with new updates and is migrated out and Centera provides new content address. Now you have file1.txt and file2.txt both on the file system and on the Centera with their own content addresses.
If original+ changes is true then the original BLOB data would no longer be valid? So if a restore was performed from a piece of backup media to the extended drive to try to retrieve the original file for some reason, would the EA information be able to retrieve the data from the Centera?
I=> If the content address is still on the Centera and you restored the file and EA's are intact which would have that Content address for file1.txt, you should get access to the Data and that link is back again. However if there is no retention and the file1.txt is deleted and the content address is deleted on the Centera and you restored only the Stub file you would not be able to access the data as the blob has been deleted.