This GFS Strategy is bugging me as there is no defintive answer to how many tapes to buy. So how many does it take to get to the center of a tootsie pop? So many different numbers for a GFS Routine it is nuts. I have read anywhere from 12 to 19 and neither adds up. Considering that GFS has been around since my Grandfather, one would think someone would have a number of tapes. Now I have to convince my supervisor that hey we need X=Number of LTO-4 Tapes * 2 at the cost of $30.00 a cartridge. The rub is you can't overwrite tapes each day or you don't have a backup to go back to. So what do you tell your supervisor?
O.K. when it comes to backup's I am a belt and suspenders type of guy. Screw incremental and the partials. I want a full backup of my users data every night. Here is my GFS rotation
Monday - Thursday = Son = 4 tapes. I would like to keep the Son a full daily set until the Father is run on Friday = 1 x rotating back after 26 days days. On the 1st Saturday of the month I run Grandpa and want to keep these tapes for a year. 12 tapes. Sunday I run other maintenance programs, do scans and on the 7th day the tape backup rests. My library can hold 28 tapes plus a cleaning tape. I know 29 is an odd number but add a mail slot and you get 30.
In order to do a complete backup of user data takes 2 LTO-4 tapes. So mmultiply by 2. It would be favorable to have an extra 4 daily tapes so 4 tapes don't get run into the ground.
So I need 24 tapes for the Granfather = rotate out every month to keep off-site. 8 Tapes for the Father 6 can't be touched for 4 weeks and 8 tapes for the son. But these tapes can't be touched for 5 days. So I have to rotate in 2 new tapes for the grandfatehr each month. My library holds 31 tapes. So I would have 8 tapes tied up for 6 days, 14 tapes tied up for 28 days which = 20 tapes in limbo givining me 11 tapes to have on ready for each full backup and to keep any tapes from over use. Golly I hope we don't nee to have 3 tape backups.
Bear in mind I want full backups for as long as I can get my users data backed up. I am open to any suggetions, changes - except full backups, ideas or a better way. Although, we already bought into this system so don't tantilize me with SANS and constatnt backup.