[kwlug-disc] Backup and Recovery in the 21st Century

Khalid Baheyeldin kb at 2bits.com
Tue Jan 12 11:09:30 EST 2010


On Tue, Jan 12, 2010 at 9:46 AM, Adam Glauser <adamglauser at gmail.com> wrote:

> Khalid Baheyeldin wrote:
>
>> The fact that it works on the file system level also has advantages. You
>> can restore a partition EXACTLY to what it was before. This means
>> timestamps, ownerships, access times, ...etc.
>>
>
> Is the main advantage over using --archive with rsync that the backup can
> reside on a filesystem that does not support all the features of the source
> filesystem?


Rsync as most people use it is not real backup. You have only one copy on
another machine (which is good), but you don't have versions. You just have
the latest sync point in there.

Rsync here is like RAID, it protects from one thing only (disk failure in
case of RAID, and machine failure in case of rsync). What they do not
protect against, is user error, e.g. someone deletes a file by mistake then
realizes it a week after, or an application bug corrupts data and you
realize that after 4 days.

With Rsync and RAID, you are out of luck. If you have real versioned backup
you can go back and retrieve your file from the older backup.

I have had a few instances of "oops!" and had to go to backup and found what
I deleted in it. Rsync and RAID do not provide that.

I am not saying that dump is the only such program. If you write a script to
do tar or cpio archives to another machine, then you have versioned backups.
But with dump you can do incremental and between the full and (say) a 6
incremental, you can go back and get anything from backup. If you leave a
monthly or quarterly full then you are better too.

This is why I linked to the Tao of Backup because it explains what backups
should be. RAID and rsync do not do everything proper backup does.
-- 
Khalid M. Baheyeldin
2bits.com, Inc.
http://2bits.com
Drupal optimization, development, customization and consulting.
Simplicity is prerequisite for reliability. --  Edsger W.Dijkstra
Simplicity is the ultimate sophistication. --   Leonardo da Vinci
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