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Re: Backups - was: Re: LVM

On Tue, 15 Jun 2010 11:32:15 +0100, Lisi wrote:

> On Tuesday 15 June 2010 01:25:56 Andrew Sackville-West wrote:
>> There are many many ways to make take backups beyond having a disk big
>> enough to hold the data.
> Would you feel inclined to elaborate?  I'm trying to solve this problem
> for my granddaughter's large HDD, and am not keen to have to buy a 300GB
> external drive.  Tar would still require a fairly large medium. :-(

I would differentiate between "backup" data and "archived" data.

By "backup" I see a copy of the current files in the system and as per 
"archived" data I understand it as several snapshots of the data taken in 
different days and so holding different data.

Backup usually takes less space than archival, but sometimes archival is 
necessary (a "must have" in a company).

The most common procedure for a user's POV in order to get a data backup 
is by using a "differential" backup with some kind of compression. The 
first copy of the data will take all the files the user has selected to 
be backed up but the rest of the times the copy is only 
"differential" (only new or modified files are selected to be copied).

This way (by using a differential backup strategy) you need less space in 
the medium (the first copy is big, but the rest of the differential 
copies are of small size and so the copy procedure is very quick).

There are also those called "incremental" backups, but I find it a bit 
more complex to manage that "differential" ones, as per data restoration: 
with a differential backup yo only need the first big file and the last 
differential copy, but in order to restore from an incremental backup you 
need the first big file plus "all" the incremental ones).

As per the programs to make backups... I still use "tar" (:-P) but 
"rsync" is said to be one of the most mentioned/preferred for this task.



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