Damaged files on HDD and no any information about it from OS

[cineknt]

Hi. I would like to present my today situation and ask a few questions how to prevent damaged data.

1. I have one disk A, which have my data.
2. I have also second disk B, which I use to backup my disk A (by using FreeFileSync application).
3. Today I changed filesystem from ntfs to ext4, but it is not that important. It is important that I copied all files from disk A to empty disk B. It was about 300GB data.
4. I heard a strange noise from disk B. Windows and FreeFileSync didn't say anything about any problems. Everything looked fine, all files were copied.
5. But I was thinking about this strange noise and I decided to compare all files between disk A and disk B. Comparing was like md5 checksum, every bit compare. There is an option to do that in FreeFileSync.
6. And BANG: a few files on disk B was damaged! And it is a shock for me. So what is the point of making backups?...

I always thought I get information from operating system when something goes wrong or information like "I can't write file", "the file has been saved incorrectly". There are features like SMART etc.

My questions:
1. So even I have two disks I have no warranty that files are not damaged, do I?
2. How can I know or check that files on disk A are not damaged?
3. Should I always compare all data, bit by bit, between these two disks? Is it only way? It takes a lot of time...
4. Are there any official methods to do backups? How do companies solve this problem?
5. If some company have files like very important databases, how they are sure that their files are not damaged? They may have a situation like mine, e.g.: user creates an bank account, server saves data on disk, and bang, data are damaged (in extreme situation the user may have 1000000$ instead of 0$).

[craig6928]

always remember to do a full format of your drive before using it when buying from new
as this removes any bad sectors
all new drives have bad sectors


its more likely the data landed on a bad sector on the drive
the only time you might get a warning is when its writing and it comes up crc error
that is a time to backup

also its more down to your FreeFileSync application that could had corrupt your data
but again you might have a error on drive a also

what os are you using

it can happen to anyone happen to us once

i recommend you get a copy of a program called teracopy

http://codesector.com/teracopy

this will do a 100% clone of all your files and make sure that they are correct byte
if it fails it will come up in the list with failed file transfers

smart is not that reliable in the bios

only way your find out when smart file is when your drive does not work
or you run a harddrive test tool


4. Are there any official methods to do backups? How do companies solve this problem?

companys will backup there data in a way where they dont delete the other backup

they have two main backups of there data base or mirror the image as its called.

to a raid system normal a set of 6 drives that are doing mirror image
if one fails then the other one kicks in

but to tell the truth we had raid system in where they all failed lol
as the faulty drive copied over the good one




you ask

Should I always compare all data, bit by bit, between these two disks? Is it only way? It takes a lot of time...

yes you should but if the file size is correct it should be fine


buy teracopy this will check the data on transfer and will tell you if the file is corrupt or damaged



2. How can I know or check that files on disk A are not damaged?

well for a start dont run checkdisk or your data would go byebye
only true way is to open the files up.
if a file is damaged sometime the structure might be changed


end of the day it does not matter how you backup

if its going to fail its going to fail both ways

important files or photos backup to dvdr

online storage are ok but they do tell you in the terms
that if your data is gone or its been deleted
you can not sue them

[digitalferret]

thanks for teracopy link craig.

codesector seems to be down tho: checked via http://isitdown.co.uk/

maybe try
http://www.filehippo.com/download_teracopy/

as alternative if needed.

edit: uh-ho maybe other issues. Some other international sites down as well from here.
#Gremlins