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    StorageExpress(TM) System: Grandfather-Father-Son Backup Strategy

    
    

    STORAGEEXPRESS(TM) SYSTEM: GRANDFATHER-FATHER-SON BACKUP STRATEGY

    
       GFS (grandfather, father, son) is the tape rotation strategy used in the
    
       StorageExpress system's Streamlined backup. GFS simplifies tape handling
    
       by organizing rotation into daily, weekly, and monthly backup tapes. You
    
       can also create Custom backup jobs that use the GFS strategy.
    
    
    
       Why GFS?
    
       LAN administrators consider GFS one of the simplest and most effective
    
       tape rotation strategies.
    
    
    
       The GFS tape rotation strategy provides several benefits:
    
    
    
         *  It protects your data with a minimum number of tapes (normally,
    
            only one or two tapes are required to restore a file server),
    
            rotating some tapes and archiving others, so you can easily restore
    
            one file or an entire file server.
    
    
    
         *  It reduces wear and tear on tapes and tape heads.
    
    
    
         *  It provides a systematic approach to tape storage that ensures the
    
            highest possible protection for your data and gives you an easy way
    
            to locate stored files.
    
    
    
         *  It maximizes File Tracker use while keeping down the File Tracker's
    
            size.
    
    
    
       The File Tracker is a database that stores information about every file
    
       on every backup tape created by the StorageExpress system (except
    
       Tape-to-go and Self-backups). This makes restoring directories and
    
       volumes fast and easy.
    
    
    
       What is GFS?
    
       The GFS tape rotation strategy is based on a 7-day schedule (Sunday
    
       through Saturday), in which you create at least one full backup each
    
       week. The rest of that week's backups can be full or differential. (A
    
       differential backup saves only the files that changed since the last
    
       full backup.)
    
    
    
       Regardless of the number of full backups you create during the week, the
    
       LAST full backup of the week is considered the WEEKLY backup. You can
    
       reuse (recycle) the DAILY and WEEKLY backup tapes or take them offsite
    
       for permanent storage. For a discussion of when to reuse tapes, see Tape
    
       Recycling later in this document.
    
    
    
       Here are some examples of weekly backup schedules:
    
    
    
       EXAMPLE 1
    
    
    
       SUN     MON    TUES    WED   THUR    FRI   SAT
    
       ---     ---    ---     ---   ---     ---   ---
    
       None    Diff*  Diff    Diff  Diff    FULL  None
    
    
    
                                    *WEEKLY*
    
    
    
       EXAMPLE 2
    
    
    
       SUN     MON    TUES    WED   THUR    FRI   SAT
    
       ---     ---    ----    ---   ----    ---   ---
    
       Diff    Diff   Diff    Full  Diff    Diff  FULL
    
    
    
                                            *WEEKLY*
    
    
    
       *Diff=Differential backup
    
    
    
       In GFS terminology, the DAILY backup is the son and the FULL WEEKLY
    
       backup is the father.
    
    
    
       The last full backup of each month is considered the MONTHLY backup. In
    
       GFS terminology, it is the grandfather. The MONTHLY backup is always
    
       permanent--it cannot be reused. It's a good idea to store permanent
    
       tapes offsite.
    
    
    
       The following is an example of a typical backup schedule. 
    
    
    
       MONTH 1
    
    
    
       SUN       MON       TUES      WED       THUR      FRI       SAT
    
       ---       ---       ---       ---       ---       ---       ---
    
       1         2         3         4         5         6         7
    
       None      Diff*     Diff      Diff      Diff      F-WKLY**
    
                 Tape 1    Tape 2    Tape 3    Tape 4    Tape 5
    
       ---       --        ---       ---       ---       ---       ---
    
       8         9         10        11        12        13        14
    
       None      Diff      Diff      Diff      Diff      F-WKLY    None
    
                 Tape 1    Tape 2    Tape 3    Tape 4    Tape 6
    
       ---       ---       ---       ---       ---       ---       ---
    
       15        16        17        18        19        20        21
    
       None      Diff      Diff      Diff      Diff      F-WKLY    None
    
                 Tape 1    Tape 2    Tape 3    Tape 4    Tape 7
    
    
    
       ---       ---       ---       ---       ---       ---       ---
    
    
    
       22        23        24        25        26        27        28
    
       None      Diff      Diff      Diff      Diff      F-MTHLY   None
    
                 Tape 1    Tape 2    Tape 3    Tape 4    Tape 8    
    
       ---       ---       ---       ---       ---       ---       ---
    
       29        30        31
    
       None      Diff      Diff
    
                 Tape 1    Tape 2
    
       ----      ---       ---
    
    
    
       MONTH 2
    
    
    
       SUN       MON       TUES      WED       THUR      FRI       SAT
    
       ---       ---       ---       ---       ---       ---       ---
    
                                     1         2         3         4
    
                                     Diff      Diff      F-WKLY    None
    
                                     Tape 3    Tape 4    Tape 9
    
       ---       ---       ---       ---       ---       ---       ---
    
       5         6         7         8         9         10        11
    
    
    
       None      Diff      Diff      Diff      Diff      F-WKLY    None
    
                 Tape 1    Tape 2    Tape 3    Tape 4    Tape 10
    
       ---       ---       ---       ---       ---       ---       ---
    
    
    
       * Diff=Differential backup
    
    
    
       **F-WKLY=Full WEEKLY
    
    
    
       Tape recycling
    
       By default, Streamlined backup recycles (reuses) DAILY tapes after the
    
       fourth daily backup. (In the previous example, notice how tapes 1
    
       through 4 were reused each Monday through Thursday.) This four day cycle
    
       lets you restore a file to the state it was in on any of those four
    
       specific days. By default, Streamlined backup recycles WEEKLY backup
    
       tapes after the fifth full weekly backup.
    
    
    
       The previous example assumes that you've used the default Tape Recycle
    
       settings for a Streamlined backup. In this case, a full year of backups
    
       would require 21 tapes: 4 DAILY, 5 WEEKLY, and 12 MONTHLY. Of course,
    
       this number can increase when tapes are retired at the end of their
    
       useful life, or if the Tape Recycle setting is increased. For a
    
       discussion of tape retirement, see document 6720.
    
    
    
       Central Console's Tape Recycle window (available when you choose
    
       Advanced Options from the Streamlined Backup and Settings window) lets
    
       you change the the number of DAILY and WEEKLY tapes you'll use before
    
       recycling. You can increase the DAILY Tape Recycle setting to restore
    
       data from more individual days.
    
    
    
       In the following example of an eight day recycle setting, you can
    
       restore a file to the state it was in on day 2 through day 11 (day 6 is
    
       included because it's a full weekly backup). 
    
    
    
       SUN       MON       TUES      WED       THUR      FRI       SAT
    
       ---       ---       ---       ---       ---       ---       ---
    
       1         2         3         4         5         6         7
    
       None      Diff*     Diff      Diff      Diff      F-WKLY    None
    
                 Tape 1    Tape 2    Tape 3    Tape 4    Tape 5
    
       ---       ---       ---       ---       ---       ---       ---
    
       8         9         10        11        12        13        14
    
       None      Diff      Diff      Diff      Diff      F-WKLY    None
    
                 Tape 6    Tape 7    Tape 8    Tape 1    Tape 9
    
       ---       ---       ---       ---       ---       ---       ---
    
       15        16        17        18        19        20        21
    
       None      Diff      Diff      Diff      Diff      F-WKLY    None
    
                 Tape 2    Tape 3    Tape 4    Tape 5    Tape 10
    
       ---       ---       ---       ---       ---       ---       ---
    
    
    
       What if you don't use GFS?
    
       If you don't use a tape rotation scheme, the File Tracker can quickly
    
       exceed the capacity of even the largest hard disk.
    
    
    
       The File Tracker grows by 130 to 160 bytes for every backed-up file.
    
       When the StorageExpress system's hard disk reaches 80% of its capacity,
    
       it automatically prunes (deletes) the oldest file detail history. If the
    
       File Tracker has pruned data that you later want to restore, you'll have
    
    
    
       to use the slower Manual Restore option, or "merge" the tape back into
    
       the File Tracker. (Merging is the process of manually adding file detail
    
       history to the File Tracker database.)
    
    
    
       You can stop File Tracker growth by purging old tapes from it
    
       periodically. When you purge a tape from the File Tracker database, all
    
       information about that tape's file detail history is deleted. 
    
    
    
       You can manually purge tapes from the File Tracker database by using the
    
       Purge button in the Central Console's Browse Tape Catalog menu. This can
    
       be time consuming, though.
    
    
    
       The easiest way to prevent File Tracker overgrowth is to let the GFS
    
       tape rotation strategy manage the purging for you. GFS automatically
    
       purges the File Tracker database of the tape's file detail history when
    
       a tape is reused.
    
    
    
       Avoid renaming or bulk-erasing tapes
    
       When tapes are renamed or bulk-erased, the tape's file detail history
    
       remains in the File Tracker database. The File tracker database grows
    
       quickly.
    
    
    
       Use the StorageExpress system to Quick-Erase or format the tape instead.
    
       It automatically deletes file detail history from the File Tracker
    
       database, slowing its growth.
    
    

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