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Win7 with Two 2tb USB drives - only one seen

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June 11, 2010 3:26:34 AM

Hello,
I have several WD MyBook Essentials USB drives. I have been backing up a 2 tb MyBook to two 1TB MyBooks. Now, I have a second 2tb MyBook to back it up to. However, I cannot get both 2tb drives to mount at the same time. I can mount either one separately, but not together. The second one to be mounted does not show up in Explorer. Both do show up in the dismount utility in the Notification area of the Taskbar. Help appreciated. I'm running Win7 64-bit on an Acer Aspire 5536-5142 (AMD Athlon 2-core). All drives are NTFS. Thanks in advance.

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a c 415 G Storage
June 11, 2010 6:21:33 AM

I wonder if at some point you had each drive connected to the system all by itself and configured them (one at a time) to use the same drive letter. If they're both trying to use drive letter "E:" for example, it might explain why only one at a time shows up.

Plug both drives in, go to Disk Manager (Start -> Right-click "Computer" and select "Manage" -> click "Disk Management" in the left pane). Right click on the partition map for each drive (in the lower portion of the right pane) and select "Change Drive Letter and Path..." to see which drive letter is assigned and, if necessary, change one of them.
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June 11, 2010 7:17:57 PM

1809709,2,450409 said:
I wonder if at some point you had each drive connected to the system all by itself and configured them (one at a time) to use the same drive letter. If they're both trying to use drive letter "E:" for example, it might explain why only one at a time shows up.

Thanks sminlal. I did not configure drive letters for the drives. They always just take the next letter available whenever I choose to connect them. They are disconnected most of the time. I have more information about the issue. I booted the same computer into ubuntu linux. ubuntu thinks the new 2tb drive is an msdos drive while the old 2tb drive in ntfs. It did mount them both and allow me to use them. Win7 says that they are both ntfs. Yet, further investigation shows that Macrium Reflect created a series of backup files of 4gig each rather than the usual one huge file ... suggesting that it is, in fact, a FAT32 drive. Working under the assumption that something is screwed up with the formatting (even though the drive seems ok except for the filesize limitation), I have begun a hard reformat to ntfs. I am about 5 hours into the reformat and it is about 20% done. I will post back when I know if this resolved the issue.
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June 13, 2010 3:51:15 AM

OK. The problem is solved, but not all of the mystery. In the Win7 DiskManagement (put diskmgmt.msc in Start Menu search box), both drives show up, but the second one to be connected says 'Offline'. A mouse-over of 'Offline' elicits the msg: "This disk is offline because it has a signature collision with another disk." I do not know what this means, but I know the immediate solution. Right-click on the word 'Offline' and select 'Online' from the popup menu. The drive will be assigned a letter and will now function normally within Windows. Another article I read states (unofficially) that you cannot assign the drive a letter in this situation: you must allow Windows to do it.
The drives perform completely normally. After restarting Windows, the drives mounted ok. I do not need to set them to 'Online' in the disk management utility, as I had feared I might.
I have been searching for how to change the drive signature, but I have yet to find a way. Luckily, it doesn't seem to be necessary.
BTW - the hard format of my 2tb USB 2.0 drive was about 28 hours. It did not help with this issue.

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a c 415 G Storage
June 13, 2010 7:29:13 AM

OK, that makes sense. What's probably happened is that you made a clone of the drive, which caused it to have a duplicate signature. The signature is what Windows uses to distinguish one drive from another for the purposes of assigning drive letters, etc.

Here's a link that describes how to change the signature: http://www.howtohaven.com/system/change-disk-signature....
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June 13, 2010 2:48:11 PM

Well, no, I didn't make a clone. I put some files on it and then deleted them. I did nothing more. I was getting ready to copy all the video files on my first 2tb drive to the new 2tb drive just using Windows Explorer when I ran into the problem that stopped me from doing so.
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a c 415 G Storage
June 13, 2010 7:56:22 PM

Then it's hard to imagine how you would have got the same signature on both drives. I sure hope WD isn't stupid enough to pre-format all their drives with the same signature...

But at any rate the instructions in the link I posted should fix it.
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June 20, 2010 2:19:22 PM

Thanks for the link. I do not know how disk signatures are handled. Perhaps it is similar to IP addresses: a manufacturer is given a range of numbers by a controlling agency similar to the Internet Assigned Numbers Authority for IP addresses. In any case, I will not change the signature since the drives now mount correctly everytime I start the system.

I, too, hope WD doesn't create too many duplicate signatures. One of the drives in question was a referb. Why or if this should matter, I do not know.

I find this forum very difficult to use. I received 2 emails today saying that there are responses to this thread. When I click on the links, I see two of my posts, but I do not see the new replies. Using the search facility, I cannot even locate my original posts.
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February 14, 2012 5:02:43 PM

sminlal said:
...I sure hope WD isn't stupid enough to pre-format all their drives with the same signature...

They might be. I'm having the same issue right now with two WD 3TB drives right now that were purchased from two different vendors. FWIW, I've seen the same problem in the past with Seagate drives, as well as WD drives. Not sure why the manufacturers do this because I always prefer to back up a drive to a matching model drive. The 'right-click Online' solution described above *usually* works for me.

Anyway, I know this this thread is old but it's was helpful in helping me understand the situation. Thanks for posting to it.

G.
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February 14, 2012 6:39:19 PM

This topic has been closed by Mousemonkey
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