Coalwater, Very good explanation!! What you should include is that when doing a file restore from backup the difference is:
1) Since the reference point for a differential is always d0 (full backup) when doing a restore the only backup needed is the last one (plus, of course, the full backup). It is because of this that doing a restore from differential is always faster and requires less tapes/ disks/whatever. But, in the same manner, doing the backup takes longer and requires more space (on the disk/ tape/whatever). 2) Restoring from an incremental backup requires the full backup, then each and every incremental backup taken. On Jan 16, 9:07 am, Mohammad AbuShady <[email protected]> wrote: > ok so according to what i read i'll try to explain it simply > Suppose we have a computer that has files named with letters a0,b0,c0,d0,e0 > (ill assume it's 5 files, and the 0 show's it's the first version of the > file, and ill increment that number every time it gets modified) > We will perform a full backup and suppose it's on day0, now so we have a > backup that has all those files(a0,b0,c0,d0,e0) > > *Day1*, files b and e were modified. > Current files on system:a0,b1,c0,d0,e1 > > *incremental backup*:will backup only the new b1 and new e1 > *files included in incremental backup*: b1,e1 > *differential backup*: at this same point will do exactly the same (i'll > explain why later) > *files included in differential backup*:b1,e1 > > ---- > > *Day2*, files a,b were modified, > Current files on system:a1,b2,c0,d0,e1 > > *incremental backup*:we will backup the new changes compared to the most > recent backup (the one on day1) > *files included in incremental backup*:a1,b2 (e1 remains unchanged so no > need to include it) > *differential backup*:we will backup the new changest compared to the most > recent *FULL* backup (the one on day0) > *files included in differential backup*: a1,b2,e1(any thing that is *different > *since last full backup (a0,b0,c0,d0,e0) > > ---- > > *day3*, files c,e were modified > Current files on system: a1,b2,c1,d0,e2 > *incremental backup*: since last backup (day2) we have only c1,e2 with > changes > *files included in incremental backup*: c1,e2 > *differential backup*:the only file that we wont include here is d0 because > it never changed (since last *FULL* backup) but all other files have. > *files included in differentcial backup*: a1,b2,c1,e2 > * > ---- > > *So i think by now you should be getting the picture how things work, now if > we want to look at advantages and disadvantages of each. > Incremental backup: > *Adv*. You might have noticed already, the number of files we included in > the backup every day was minimum, so we could say that it has fast back up > times and also saves hard disk space (compared to both full and differential > backups) > *Dis*. Now if i need to restore the files, ill need all backups since the > last full backup till the day i want to restore to, so if i want to restore > to day5 for example, i need day0,day1,day2,day3,day4,day5 backups > > Differential backup: > now if i need to restore using differential backups, using same assumptions > (a restoration to day5) we will only need the backups day0 and day5 only. > *Adv*. fast restoration time > *Dis**, *slower backup time (compared to incremental, but it's still faster > than a full backup) because as we see at day2 i was backingup 3 files and at > day3 it became 4 files, and it will increasing the further i become to the > last full backup (day0) > > ps. about day0, the both backups were the same because the reference point > was the same (day0), incremental backups' reference point changes every day > (assuming daily backups) to most recent backup, but differential backups' > reference point stays the same to most recent FULL backup, it will only > change if you perform a full backup on any day > > Hope i was able to explain this good enough.. > > ~Coalwater~ > > On Sat, Jan 16, 2010 at 1:05 PM, Ka dadi <[email protected]> wrote: > > Hi Team, > > > Can someone put to me in plain English the difference between Incremental > > and Differential Back-up ? I read and read, and as soon as I think I > > understood, I lose it again! > > > Ka_dad > > > -- > > You received this message because you are subscribed to the Google Groups > > "Computer Tech Support" group. > > To post to this group, send email to > > [email protected]. > > To unsubscribe from this group, send email to > > [email protected]<computer-tech-support%[email protected]> > > . > > For more options, visit this group at > >http://groups.google.com/group/computer-tech-support?hl=en.
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