Getting a better handle on GFS (Grandfather-Father-Son) backups
Posted on 2013-11-04
Call this an extremely newbie question but my question is on the use of a GFS backup strategy for data. What I need to wrap my head around is what and from what time data can be recovered from. Specifically from this example: If I backup a file server with a weekly full, daily incremental and a monthly full, no matter the software and I retain every daily for one week, 4 weeks for the monthly and a single monthly and retain these for 3 years. I would in effect have 12 backups at the end of each year (not after 3 years and if the software did a yearly you would have one backup for each year, 3 yearly tapes). So now comes along a user who says they remember a file being there 3 months ago but it's not there today. So, I go back 3 months, find the file and voila, restore it and all is good BUT, now a user creates a file one day, the daily incremental backs it up, the next day the file gets deleted and is no longer a part of a backup, the weekly does it's full and the monthly does as well and 3 months later the same question comes in for the file. What I am looking for is, when a weekly is done, does it in fact take all previous incrementals and consolidates them into the weekly full OR is just taking a full snapshot of the server at that point and then the daily tapes just get overwritten thus forever deleting the file since it is not there at the end of the week? I understand if a user creates a file and then deletes it before the incremental is performed the file is gone (not taking into account CDP constant data protection and shadow copies). But, if I only have a monthly, would that file be there? Does the GFS strategy take all daily files, consolidate them into a weekly then consolidates the weeklys into the monthy so everything would be there? I hope this is not too confusing I just want to make sure that if a file is at least a part of ONE of the daily incremental backups that I can go back in 2 years and be able to restore the file. Thanks!