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#1 2012-07-26 14:46:37

Daniel_Cro
New member
Registered: 2012-07-26
Posts: 3

data corruption - important

Hello,

I have been using DNS-323 a couple of years now.
It contains two 2TB WD's EARS reformatted as required.
There is also a 32GB USB stick inside for torrent download, system files, etc...
Funplug is installed as well other utilities like fan control and cron and rsync.
Several folders on disk A are shared on Windows network such as; Video, Audio, Pictures... and mounted as drives on multiple computers in my home.
Disk B is only used to rsync (backup) complete content each night from disk A.

I have noticed recently that two movies want play, one mp3 has been corrupted (clicks in sound) and one picture corrupted (half of the picture is useless garbage).

What have happened?
rsync sensitive to corruption?
Is it a normal data degradation?

Any ideas?
Thank you!

Last edited by Daniel_Cro (2012-07-26 14:47:25)

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#2 2012-07-27 12:20:38

scaramanga
Member
Registered: 2010-08-04
Posts: 251

Re: data corruption - important

Daniel_Cro wrote:

What have happened?

Bad sectors? Imminent disk failure?

Daniel_Cro wrote:

rsync sensitive to corruption?

That depends on how you use rsync. Read about --checksum here: http://www.samba.org/ftp/rsync/rsync.html

Daniel_Cro wrote:

Is it a normal data degradation?

There's nothing normal about data degradation. Disk failure and bad sectors, on the other hand are, since HDD are mechanical devices and, as such, eventually fail. When that happens the result is data loss.

Daniel_Cro wrote:

Any ideas?

Check your backup: are the files good?
If so, you can use rsync to find which files were, possibly, corrupt, using --checksum --dry-run --itemize-changes
The files this would list should be treated as suspicious, not 100% positively corrupt, because maybe the files was changes since it was backed-up, or maybe the backup was corrupted.
This may take a l-o-n-g time time to run, depending on how much data you have. Read more about rsync and those options in the link I provided, above.

Good luck!

Last edited by scaramanga (2012-07-27 12:27:18)


DNS-323 HW Rev. C1 FW 1.10 fun-plug 0.5
2 x WD10EARS-00Y5B1 in Standard mode (LCC set to 5 min; Aligned to 4K)
Transmission with Transmission Remote GUI

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#3 2012-07-27 12:28:23

Daniel_Cro
New member
Registered: 2012-07-26
Posts: 3

Re: data corruption - important

Thank you scaramanga!

I presumed normal degradation due to read error rate usual/specified for each drive... it is low rate, but I am syncing 1TB of data each day so...

I will check the drive using your suggestions and report back in a day or two.

Thank you!

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#4 2012-07-27 15:24:23

scaramanga
Member
Registered: 2010-08-04
Posts: 251

Re: data corruption - important

It has more to do with how many changes are made, not how much data, overall, you store.
You can add the --stats option to rsync's command line for a brief summary of what rsync has done (you keep the log, right?).

Last edited by scaramanga (2012-07-27 15:32:17)


DNS-323 HW Rev. C1 FW 1.10 fun-plug 0.5
2 x WD10EARS-00Y5B1 in Standard mode (LCC set to 5 min; Aligned to 4K)
Transmission with Transmission Remote GUI

Offline

 

#5 2012-07-30 10:08:21

Daniel_Cro
New member
Registered: 2012-07-26
Posts: 3

Re: data corruption - important

corrupted data seems to exist on both disc A and disc B.
One other thing that crossed my mind is that these files are rather old... and could be corrupted from the time when my ancient hard drive failed and I have recovered data (all before I created NAS device).
If this is the case then everything is OK.
When I find time, I will check SMART status on HDD's.

Thank you!

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#6 2012-07-30 10:49:14

scaramanga
Member
Registered: 2010-08-04
Posts: 251

Re: data corruption - important

Daniel_Cro wrote:

corrupted data seems to exist on both disc A and disc B.
One other thing that crossed my mind is that these files are rather old... and could be corrupted from the time when my ancient hard drive failed and I have recovered data (all before I created NAS device).

rsync can't help you detect that, obviously, only using those files.
Or, maybe, if they're of some specific type and there's some error-detection/repair tool for that file type that you could use.


DNS-323 HW Rev. C1 FW 1.10 fun-plug 0.5
2 x WD10EARS-00Y5B1 in Standard mode (LCC set to 5 min; Aligned to 4K)
Transmission with Transmission Remote GUI

Offline

 

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