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Author Topic: Disk shows full at 1 TB but directory sizes add up to only around 647 GB?  (Read 3078 times)

bfmorgan

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Disk shows full at 1 TB but directory sizes add up to only around 647 GB?
« on: February 16, 2011, 08:51:58 AM »
Hello,

I have a DNS-323 with a pair of 1 TB Segate ST31000340AS drives in a RAID1 configuration.

I have used it for a couple of years as a pure backup drive.

Today when backing up using Norton360 I received an error that the drive was full. 

I have the disk mapped as drive Z on my system.


Using Windows Vista to check properties of the drive, I see the drive show almost full with a total size of 914GB.

BUT when I look inside the drive directory and look at properties of each directory on the drive, the total size of all added together is only 637GB.

My first thought was fragmentation, but from reading posts here it looks like the answer is either not fragmentation (at least not enough to use up 30% of the disk) or it is fragmentation and there is nothing I can do about it.

I am looking for any advice on figuring out what is wrong before I remove the drives to start looking for a solution.

I am using firmware 1.08.

I have run scandisk from the DNS-323 GUI and it showed no problems.


Any help is much appreciated. Thanks.
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MJBURNS

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  • Posts: 24
Re: Disk shows full at 1 TB but directory sizes add up to only around 647 GB?
« Reply #1 on: February 16, 2011, 05:31:05 PM »
Not to get quite off your topic, but I'll bite. What about fragmentation of the drives of a DNS-323? (Especially a RAID 1 system.) How to you ascertain the level of fragmentation? Can you defrag a DNS-323? If so, how (other than transferring the data off, erase the drives, and copy the data back)?
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lookingforinfo

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Re: Disk shows full at 1 TB but directory sizes add up to only around 647 GB?
« Reply #2 on: February 16, 2011, 06:47:43 PM »
My wife uses Norton360 on her machine and her backups are written the our DNS-323.  I have taken a quick look at the structure of the output files and is is my guess that the data is stored in a proprietary database.  I believe the backups are incremental and it would be my second guess that when a file changes, the old data records are flagged as outdated, the new data is written in a new location and pointers to the data are adjusted.  Therefore, after two years your backup file probably has many unused sectors.

An approach to see if this is true would be to delete the N360_BACKUP directory, and recreate a new backup to see how your space utilization changes.  Since you still have the files on the Windows machine, you should be fairly safe.  It will probably take about 4 or 5 hours to recreate the backup.

Please tell us what you learn.
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