Why is my back up drive so much fuller than the main drive?


M

Metspitzer

I have a 120G SSD. I am using a 160G HDD to back it up. I am using
80G on the main drive, but the HDD is using 158G.
 
S

Stefan Patric

I have a 120G SSD. I am using a 160G HDD to back it up. I am using 80G
on the main drive, but the HDD is using 158G.
My guess? The backup software is keeping the previous backup(s). That
is, it is not deleting the old backup(s) when it creates a new one.

If you are using some type of backup app, check how it's configured.

Stef
 
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S

Sam Hill

Stefan said:
My guess? The backup software is keeping the previous backup(s). That
is, it is not deleting the old backup(s) when it creates a new one.

If you are using some type of backup app, check how it's configured.
My guess: the backup drive is not using the same file system as the 'main
drive' - sector sizes, etc - and the backup takes twice as many drive
sectors. Check for use of NTFS/FAT32 differences.
 
G

Gordon

My guess? The backup software is keeping the previous backup(s). That
is, it is not deleting the old backup(s) when it creates a new one.

If you are using some type of backup app, check how it's configured.

Stef
This brings up an interesting question that I'd like some insights to.
I use an external hard drive to back up the Libraries folder from my
Windows 8 computer. I keep old copies of these backups for a while,
just in case something goes wrong with the later setup. Each time I do
a backup I just make a new folder on the external hard drive and give
it a name like 130205Pavilion...date and computer identity info. This
naming will let the latest backup be easily recognized and the older
backups can be deleted from time to time.

I then do a copy of my Libraries folder on the computer and paste it
into this new folder on the hard drive. Is this a reliable way to do
external hard drive backups? Or is there a much better way to go?

Thanks, Gordon
 
A

Asger Joergensen

Hi Metspitzer
I have a 120G SSD. I am using a 160G HDD to back it up. I am using
80G on the main drive, but the HDD is using 158G.
Well you don't say what kind of backup you are using, so it can be many
different things, some are already mentioned, but I see the same on
my backup and my reason are more simple then those already mentioned.

I use a very simple backup that just copy all changed files to the
backup drive. My backup is not set up to mirror, so when i delete
a file it is not deleted in the backup, and the same goes when I
rename a file, then i have two files. Over time id adds up, but I
got a 2TB disk, so I still go some time before I need to clean. ;-)
 
K

Ken Blake

My guess: the backup drive is not using the same file system as the 'main
drive' - sector sizes, etc


You mean *cluster* sizes. All sector sizes are the same--512 bytes.

and the backup takes twice as many drive
sectors.

No, not even if you substitute the word "clusters" for "sectors." When
you create a file, unless its size is an exact multiple of the cluster
size (which is *very* rare) all the clusters are filled except the
last cluster. On average, the last cluster is half filled, and that's
very different from saying that one uses twice as many clusters as the
other.

But your guess might be right, and the difference in space used might
be because of a difference in file system causing more wasted space in
those last clusters.
 
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S

Sam Hill

But your guess might be right, and the difference in space used might be
because of a difference in file system causing more wasted space in
those last clusters.
Yeah, thanks for adding that, and not making me look *incredibly* stupid.
 
K

Ken Blake

Yeah, thanks for adding that, and not making me look *incredibly* stupid.

LOL! I didn't want to make you look stupid. We all make mistakes, and
using the wrong term is among the easiest kind of mistakes to make. I
do it too, now and then.
 
G

Gordon

LOL! I didn't want to make you look stupid. We all make mistakes, and
using the wrong term is among the easiest kind of mistakes to make. I
do it too, now and then.
I know what you mean, Ken. I even made a mistake once. It was that
time when I though for a moment I was wrong when indeed I was not. ;-)
Gordon
 
J

J. P. Gilliver (John)

Unless the OP has a huge number of tiny files, though, I can't see a
different file system causing a discrepancy in space usage of the
magnitudes suggested. I think it far more likely (as someone else has
suggested) that his backup routine is just accumulating backups, or at
the very least keeping the previous one as well as the current one.
I know what you mean, Ken. I even made a mistake once. It was that
time when I though for a moment I was wrong when indeed I was not. ;-)
Gordon
(-:
 
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K

Ken Blake

I know what you mean, Ken. I even made a mistake once. It was that
time when I though for a moment I was wrong when indeed I was not. ;-)

LOL!
 

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