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Old 01-11-2013, 11:09 PM
routerguy routerguy is offline
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Default Data loss issues

Hi guys,

I am experiencing issues with a Seagate Expansion Desktop, that is attached to my RT-56U via usb. I am currently in the process of backing up my entire DVD collection to HD, but every time I unplug my external disk from the RT-56U and plug it into my laptop USB, Windows 7 tells me that something isn't right with the external drive and that it has to be fixed. As a result, I am losing one or several of the DVDs I have copied and can start over again.

Here are the exact specs:
- The Seagate is a 3T drive, formatted NTFS.
- The RT-56U is running Padavan's custom firmware.
- The computer is running Windows 7 64bit.

My main issue is that I really have no clue which tree to bark up at. Is this an issue with the hard drive, or is the problem with the router that is writing to the disk?

And: I also don't know if this issue already occurs while the disc is still plugged in with the RT-N56U, or if I'm deliberately causing it by unplugging the drive. It *appears* like all is fine when the drive is still connected to the router, and after connecting it to my computer, it is not (directories missing before I start the repair process). When I manually start chkdsk, it will list most of the directories that aren't showing up, but after the repair process they are gone anyway.

It also appears like the issues are only with the more recent folders I have copied. So let's say I've just run chkdsk, couple of folders lost, but the remainder on the disk is "safe" - if I repeat this the next day, there might be issues with some of the newer folders, but not with the old ones. (And note that "new" is relative and also applies to any DVDs I might have copied the night before.)

Any pointers, ideas or suggestions would be greatly appreciated!
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Old 01-12-2013, 10:08 AM
wanttotree
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padavan fw is dont play nice with ntfs formatted drive. your solution is either format it to ext3/ext2. or you can use asus' stock firmware.
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Old 01-12-2013, 10:52 AM
Guz Guz is offline
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OK, I use NTFS with Pavadan's firmware without issue. It took me awhile to figure it out, but here is what I've found to keep the drive happy.

1. Don't every "just unplug" the drive from the router. ALWAYS use the web interface and select "Safely Remove Disk", when it says it's OK, then unplug the disk.

2. Get the UPnP Media Server files off the NTFS drive. That is, get the hidden ".dms" directory and it's contents off the NTFS drive. The easiest way is to go get a really cheap, small thumb drive, format it as ext2, put it in the "top" USB port, turn on UPnP Media server, then connect the NTFS drive. Then go back and configure the UPnP Media Server to just look at appropriate directories on the NTFS drive.

3 (optional). Use the above cheap, small thumb drive for "Torrent Transmission". Turn off Transmission, via the web interface, and then move the "transmission" directory from the NTFS drive to the ext2 thumb drive. Go back and turn on Transmission via the web interface.

If you have previously enabled Media Server with just the NTFS drive connected, I would just recommend that you take the drive back to your computer and re-format it as NTFS and start fresh. That darn ".dms" directory and it's contents can be pain to get rid of.

But once I used the thumb drive to contain the Media Server cache and database files, I haven't lost a file, nor does it need a chkdsk whenever I take it back to my laptop.
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Old 01-12-2013, 01:52 PM
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Thanks for the replies. I've already figured it out and the correct answer is #1 "Don't ever just unplug the drive from the router".

At least that seems to fix any issues for me.

I would still be curious to learn what's going on and why I always (!) lose data when I unplug the drive without "safely removing" it. Is this a cache thing? Right now I am assuming that, after copying a lot of data, I should intentionally hit "remove safely" to make sure my data is actually properly stored on the drive, and doesn't get lost at a later time when someone accidentially pulls the USB plug. I am further assuming that, if I copy no fresh data in the meantime, I can unplug the drive all I want without losing any additional files.

EDIT: Oh and does this also mean that, if there's a power outage, I must assume that last night's backups will get corrupted?!

@ Guz: Could you elaborate on the issue with the .dms folder? What problems does it cause for you?

Last edited by routerguy; 01-12-2013 at 02:59 PM.
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Old 01-13-2013, 12:52 PM
Guz Guz is offline
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Yep, it's a cache thing. Technically its a journaling issue. NTFS on it's native O/S (Windows) keeps a journal backup for sudden power failures and is able to recover when the power comes back.

The problem is NTFS is a proprietary disk format, owned by Microsoft. The NTFS driver used by the router is a reversed engineered bit of code, which doesn't quite duplicate everything properly.

If you wait long enough before just unplugging the drive from the router, it will clear it's cache and make sure the data is written to disk. Sorry, but I don't know what the exact time period is.

As for the hidden ".dms" folder...

The media server program creates a database file of all the files it finds and is able to serve out. And it also caches album art from MP3's. The album art cache is the culprit. How it extracts the album art and creates thumbnails and the directory structure for some reason it isn't 100% compatible on an NTFS formatted drive.

I haven't delved into the exact reason why. I just know that if I turned off the media server, properly unmounted the drive, took it back to a windows machine and try to delete the .dms folder I kept getting errors of access denied on various sub-folders. If I went and renamed the folders (making them shorter) I was able to delete some of them. Other times I couldn't even rename them and they were stuck. I had to then manually run a chkdsk /f and let it fix the drive to try to delete the remaining folders. A couple of times, even that didn't work. I had to copy the files I really wanted off the drive, format the drive, then put back the stuff I previously copied off.

By chance I found a little thumb drive in one of my drawers and was using it to experiment with the router. I just stumbled on formatting it to ext2, putting in on the router first, turning on the media server, etc. Like I said, since I've done that, things are working really well with attached drives.
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Old 01-13-2013, 01:03 PM
routerguy routerguy is offline
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Quote:
Originally Posted by Guz View Post
Yep, it's a cache thing. Technically its a journaling issue. NTFS on it's native O/S (Windows) keeps a journal backup for sudden power failures and is able to recover when the power comes back.

The problem is NTFS is a proprietary disk format, owned by Microsoft. The NTFS driver used by the router is a reversed engineered bit of code, which doesn't quite duplicate everything properly.

If you wait long enough before just unplugging the drive from the router, it will clear it's cache and make sure the data is written to disk. Sorry, but I don't know what the exact time period is.
Thanks for the thorough explanation. My nightmare scenario is that I have a disk failure on my laptop, then happily plug in my backup disk and notice only a moment too late that, by doing that, I have just destroyed the backups as well. My backups are going to a single-file truecrypt container, so I'm just not sure what what would happen if just a single byte of that one gets corrupted through the NTFS issue you described.

Is my conclusion right that it would be safer then to go with a disk format other than NTFS?

Quote:
I haven't delved into the exact reason why. I just know that if I turned off the media server, properly unmounted the drive, took it back to a windows machine and try to delete the .dms folder I kept getting errors of access denied on various sub-folders. If I went and renamed the folders (making them shorter) I was able to delete some of them. Other times I couldn't even rename them and they were stuck. I had to then manually run a chkdsk /f and let it fix the drive to try to delete the remaining folders. A couple of times, even that didn't work. I had to copy the files I really wanted off the drive, format the drive, then put back the stuff I previously copied off.
But did you actually lose data, or did this "only" cause major inconveniences?
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Old 01-13-2013, 01:23 PM
Guz Guz is offline
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Personally, I haven't lost any data (knock on wood) yet.

Honestly, I wouldn't use this as backup via network. I would unmount the drive, connect it to my laptop directly, then run the backup software.

This thing is just what I call a "convenience" device. It's convenient to have various files on the network. Even if you change the disk format to ext2/3/4 I wouldn't trust it.

The "gotcha" with using ext2/3/4 format is that it isn't natively supported by a windows client. That is, if you unmount the drive from the router, and plug it into your windows laptop, it won't be able to read it until you install a driver (and it's a PAIN IN THE ARSE to get Windows to read Unix drives, in my opinion).

If you want something to run network backup's to, build a server or get a real NAS device.

To be honest, a server could be just another windows XP machine with file sharing turned on, it will be more robust than the router for sharing files, IMHO.
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