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Author Topic: Storage Usage being mis-reported  (Read 1844 times)

YourBPO

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Storage Usage being mis-reported
« on: January 06, 2016, 10:40:34 AM »

Hello - I have a DNS-340L, with 4 WD Caviar Green 2TB drives in, configured as RAID5. In theory this ought to be providing about 5.5TB of storage for us.

I am copying a large number of small files to the drive as backup for our document processing facility. However, I have nowhere near 1TB of actual data on this entire network, closer to 250GB total. However, as I am copying information across to the drive, it is filling up much faster than it ought to be. I am running the latest version of the firmware, and I can't see any reason it would be doing this - I have already removed the data, updated firmware, reset the system, re-formatted again as RAID5, and started copy over and it's just happening again. The first time it would not allow me to copy anything after a certain point as the drive was 'full' (with less than 200GB copied over thus far), this time it is filling up again just as rapidly.

Here's the screenshot of the ShareCenter web app, under Management, System Status, System Info, Volume Info:
(tried posting a screenie but did not work, here's what it says instead:)

Volume Name  Volume_1
Volume Type  RAID 5
Sync Time Remaining  Completed
Total Hard Drive Capacity  5537.6 GB
Used Space  3045.8 GB
Unused Space  2491.8 GB

Here's the screenshot of a windows folder view of one of the subfolders on the drive:
(and again, screenie will not post, so here's what Windows reports:)

Size: 140GB
Size on Disk: 115TB
                that's terabytes on that second line - I don't even have that much storage on the device!

Any ideas what's happening or suggestions on how to resolve it?

When I say a large number of small files, I mean tens, if not hundreds, of thousands of 35-70kb TIFF images, and then lots of other single/multi page PDFs and various small text files. All are broken down into subfolders and there's not more than 1000 fiels per forlder, it's just how one of our systems manages raw data. But I did all this on a RAID1 mirrored BuffaloNAS nad had no issues.

Is it something to do with the RAID5 setting and how parity is written across drives? Is there a better way of having some redundancy with this ShareCenter while still being able to use as much storage space as I can?

Thanks in advance!
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ivan

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Re: Storage Usage being mis-reported
« Reply #1 on: January 07, 2016, 01:39:25 PM »

And now you see one of the drawbacks of RAID 5 - very large numbers of small files overflow the parity record space and so give very strange results.

You have proven that RAID 1 will do the job that you have of storing all these small files so why not use two RAID 1 arrays in your 340L?  While this will reduce your total array capacity it will give better restoration options should a disk go down.

While we don't have a 240L we do have several 343s and 345s all setup with two RAID 1 arrays each with 4 of them doing something similar to what you want to do - in our case store thousands of small files of parts lists, diagrams and other service information including scans of hand written notes about each job.
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stutzjr

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Re: Storage Usage being mis-reported
« Reply #2 on: January 08, 2016, 02:10:28 AM »

I don't have any kind of RAID setup in my system.  I currently just have a single drive in my DNS-340L while I am still waiting to put in some more drives.
On my Windows 10 system I also see a similar issue: file properties for "size" and "size on disk" differ wildly for files on the network drive.

Example 1:
size: 19.6 MB (20,596,926 bytes)
size on disk: 4.00 GB (4,294,967,296 bytes)

Example 2:
size: 29.4 GB (31,657,275,227 bytes)
size on disk: 4.00 GB (4,294,967,296 bytes)

Example 3:
size: 6.85 KB (7,017 bytes)
size on disk: 4.00 GB (4,294,967,296 bytes)

there's a pattern here...
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ivan

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  • Posts: 1454
Re: Storage Usage being mis-reported
« Reply #3 on: January 08, 2016, 02:43:34 PM »

stutzjr, to be able to see if there is a pattern and it is not just win10 doing strange things, you would need to do the same test with another operating system and/or use enable the FTP server on the 340L and then use FileZilla to see what file sizes it shows.
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