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Old 07-27-2010, 08:22 AM   #11
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Default Re: Your guys opinion on how best to back up?

If The OP is still about... Which is a long shot... (2 months later) -but I'll post anyway since it might help others...

I've recently discovered a new backup method that will be perfect for use in this situation. it's something we've just implemented at work, and it's pretty damned slick.

Delta backups.

Basically, it's a kind of new type of backup.

you have your traditional backup methods.

Full backup, (where everything is backed up)
and differential backups (where things that have changed since the last backup) are backed up...

now there is a new type, called Delta backups.

it's a bit like a differential backup, but also really different, and from my understanding of the technology, actually fits your problem perfectly.

I'll explain how full and differential backups work first.

lets assume you have 1000 word documents that are each 100 MB in size. (so the total data size is 10GB).

you start off with a full backup (backup everything), that takes up 10GB of tape or disk space.
the next day you do a full backup, that takes up an additional 10GB of space.
the next day you do another full backup and another 10GB of disk space is used and so on...

after 4 days you've got 40GB of used space, but on the plus side, if a user accidentally deletes a document on Friday morning, you can restore from the backup on Thursday night, then you figure out that the reason that they deleted it was that they made a mistake in it and messed it up. and you can restore from Wednesday night instead.

full backup everyday backs up everything in full.

a differential backup works a little differently.
you start with a full backup.
that's 10GB

if nobody changes anything on day 2, nothing is backed up, there are no changes so you can restore to that point in time anyway.

lets say on day 3 a user changes 10 of the 100MB documents
on day 3 the backup will backup those 10 documents, so the total backup for day 3 will be 1 GB.

if on day 4 users make a simple change to all 100 of the documents, then the total backup will be 10GB

so you've got the first backup (10GB) plus the 10 changed documents from day3 (1GB) plus the 100 changed documents from day 4 (10GB)

that's only 21GB of disk space...

and it's clearly going to be a lot easier to pull 1GB down your bosses ADSL line so you can keep an offsite backup than it is to try to pull 10GB down every night.

now, Delta backups are even smarter and even cooler.

they backup files, but they don't just look at the time the file was backed up, they look at files on a block level...

as always, day 1 starts with a full backup.

we'll keep the same scenario going, on day 2, nobody makes changes, so there is no backup data.

as before, on day 3 someone changes 10 documents, we'll say that they add a disclaimer to each, so it's an extra 1k of text.
this time rather than backing up the 10 100MB documents, (1 GB data) that the differential backup does. the backup software backs up the 10 1k change blocks, so there is only 10K of data going to your backup disk.

on day 4, there all 100 document changes, lets say that there was a mistake on the document template that generated the documents and you've had to capitalise a letter on the first page of each, that's an 8bit change, there are a hundred of these changes, but still the delta copy only copies change blocks in the file structure.

so your backup for day 4 will be 800 bytes. (less than 1k).
your total backup size is 10GB for day 1, 10k for day 3 and 1k for day 4

your initial backup is always going to be a problem over an ADSL line, but there are two things you can do about this.

you can either start the backups in the office, so on day 1 you're doing backups over your structured network. and they are really quick, then you take the server to your bosses house and they backup only the small file block changes which take no time at all...

or you just let the backup run from your bosses home...

yes that initial backup will take ages, and will saturate their line, but, it's only going to happen once.

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