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We use Truecrypt for encryption in my company, however recently an employee has got quite the odd problem.

Every once in a while when he boots his Vista pc, it changes the harddisk numbers.

This is a huge problem, because Truecrypt has encrypted partitions on two harddisks (two physical drives), however when the harddisk numbers change truecrypt can no longer "mount favorite", which remembers the numbers as they once were.

Essentially he has:

harddisk(0)\partition(2) encrypted
harddisk(1)\partition(0) encrypted

So when it swaps numbers, it suddenly reads

harddisk(0)\partition(0) encrypted
harddisk(1)\partition(2) encrypted

I've tried looking through the BIOS and disk management to no avail.

Any ideas why Vista does this ?

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4 Answers

Couldn't figure out how to do a comment, when I haven't got an openID login, so I hope it's okay it's posted as an answer.

Anyway the disks are both SATA, so there's no master/slave/cable select jumper, since there's only one cable per disk.

The one with 3 partitions are on SATA1 port, and the other is on SATA4. (In BIOS it says so, and it matches the motherboard)

It's a custom built machine, that has just recently got a second harddrive for backup purposes (should the primary disk crash).

The fun thing is, most oftenly the 3 partition disk (which is on SATA1 port) is seen by windows as harddisk(1), and this was also the case when the partitions where mounted, so this is what's desired.

I'll try switching the cables on the motherboard, and see if it changes anything.

As for BIOS settings for boot delay or powerOn or similar, there are no such settings in this BIOS :-(

If all else fails I'll just have to order a different motherboard for him, and see if it fixes it. (His collegues who use different motherboards haven't any issues)

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I swapped the cables around yesterday, and haven't seen any issues so far - however as it is random, it could take any amount of time, before he experiences the issue again. Should I somehow close this question ? (I'm new at server fault) –  Lars Jun 4 '09 at 5:02
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I've had issues similar to this in the past when using drives set to "Cable Select" when some drives don't spin up immediately on boot. Its an extreme solution, but try cracking the case and turning off drive select. If its an OEM system, they've likely left it on that setting, since its easier for them to do.

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Could it be that your HD with the 3 partitions is a slow starter? try enabeling PowerOn or Boot delay in your BIOS.

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I belive the 3 partition drive is the faster of the two, however I'll try checking his BIOS for the options you mention. –  Lars Jun 3 '09 at 9:48
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Just a quick thought:

Is any of the drives external or are there any other external drives that are sometimes attached to the unit? Are they sometimes powered on during boot and sometimes powered off?

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I forgot to mention that, my bad. Both drives are internal and only power off when not used for 20 minutes in Vista (default power settings). Both are powered during every boot, and have never been removed from the pc. –  Lars Jun 3 '09 at 8:24
And the user has no other external drives that he sometimes plugs in? I have a similar problem where the internal drives get different id's when my external sata drives are connected. –  Console Jun 3 '09 at 9:46
Not any eSate or similar, he is using USB sticks, but he always connects those after he mounts his drives (I told him to do so, because the USB stick will grab the driveletters otherwise :-D) –  Lars Jun 3 '09 at 9:47
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