Is it safer to split backups into smaller chunks?

  • Thread starter Thread starter Peter Frank
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Peter Frank

Hi,

My backup program allows me to split up the backup files into pieces
whose size I may choose.

Regardless of media and OS limits, I wonder:

Is it safer to split the backups into smaller chunks of around 50 MB
or is it just as safe to create big files of 4-5 GB filling a DVD-RAM?
(The data to be backed up have a size of around 20 GB.)

Are bigger files more prone to becoming corrupt/damaged? Is it more
likely that one out of the many 50 MB chunks will become corrupt or
that one of the few very big files will?

Regards,
Peter
 
Peter Frank said:
My backup program allows me to split up the
backup files into pieces whose size I may choose.
Click to expand...
Regardless of media and OS limits, I wonder:
Click to expand...
Is it safer to split the backups into smaller chunks of around 50 MB
or is it just as safe to create big files of 4-5 GB filling a DVD-RAM?
(The data to be backed up have a size of around 20 GB.)
Click to expand...

It is safer to use the small files if the restore mechanism
can handle a missing file. If it cant, its a waste of time.
Are bigger files more prone to becoming corrupt/damaged?
Click to expand...

No. The problem is that if the restore system can handle missing files,
you lose less if you cant get one file off the media when you need it.
Is it more likely that one out of the many 50 MB chunks will
become corrupt or that one of the few very big files will?
Click to expand...

When you get a problem with the DVD-RAM media, it shouldnt
affect too much of the DVD so you should lose less if you have
lots of small files, you should only lose the one.

It would be even better to duplicate all backups, that way you
shouldnt lose the same two files even if you do end up with an
error on two different DVDs. You should be able to get a good
complete set off both copys if you use small files.
 
Previously Peter Frank said:
Hi,
Click to expand...
My backup program allows me to split up the backup files into pieces
whose size I may choose.
Click to expand...
Regardless of media and OS limits, I wonder:
Click to expand...
Is it safer to split the backups into smaller chunks of around 50 MB
or is it just as safe to create big files of 4-5 GB filling a DVD-RAM?
(The data to be backed up have a size of around 20 GB.)
Click to expand...
Are bigger files more prone to becoming corrupt/damaged? Is it more
likely that one out of the many 50 MB chunks will become corrupt or
that one of the few very big files will?
Click to expand...

The damage probabiluty is usually per bit or per sector, i.e.
the file size does not really matter. Also an error in a
file will usually not make what comes after unreadable, unless
it was compressed with a stream compressor or encrypted.

So, no, using smaller parts will not give you an advantage.

One thing you can do is to add extra redundancy, i.e.
an error correctin code (ECC) in an extra file. There are
tools that allow you to reconstruct a smaller number
of defective sectors, while obly requiring a resonable
amount of additional space. They are intended to secure
backups and long-term storage.

Personally I have not needed them so far, since my backups
are on MOD and have been for the last 8 years. Never any
problems. DVD-RAM should be allmost as reliable.

Possible tools are "ICE ECC" for windows or "DVDISASTER"
for Linux.

Arno
 
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