What’s with drive letter A: (Windows 10 22H2)?

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[SupremeLaW]

This topic is intended for Windows 10 gurus who have not enjoyed enough complexity today, and you’re yearning for more  🙂

A probable bug deep inside Windows 10 appears to be mismanaging drive letters A thru Z.

For me, this bug first appeared after Susan strongly recommended updating Windows to 22H2.

On one of our Windows 10 PCs, that Windows Update simply would not complete successfully, no matter how many different ways we tried.  There’s a very long thread somewhere in this Forum with all the dirty details of that Windows adventure.

During our many attempts, we did notice that network drive letters were being scrambled by that major Windows Update.  So, that was a strong symptom of an OS bug buried ultra deep.

Most recently — over the past few days — we’ve been moving a SSD enclosure from an obsolete PCIe 1.0 PC to a much newer HP Z240 tower workstation.

That SSD enclosure hosts 6 x 2.5″ SSDs — one of the excellent products from IcyDock.

Without thinking there might be serious problems with drive letter A:, we temporarily assigned drive letters to A: and B: to a WDC HDD stored inside an external USB 3.0 enclosure.

This resulted in the kind of havoc that produces symptoms totally unrelated to drive letters A: and B: .

Just to illustrate, Task Manager started showing 100% utilization on several different SSDs simultaneously.

Then, RESTART and “This PC” stopped working.  From that point forward, the only way out of that situation was to hit the Power Button and hold it there until the motherboard BIOS finally SHUTDOWN.

Power-cycling the motherboard also resulted in intermittent failures:  the most annoying thing was a warm RESTART that booted up correctly, no mas problemas!

BECAUSE THE SYSTEM DID BOOT CORRECTLY, SOME TIMES AND SOME TIMES NOT, there was no warning nor any hints that drive letters A: and B: might be the culprits.

If anyone else has experimented with drive letters A: and B: (which were originally assigned to floppy disks in another ancient century), I’d love to share some war stories with you.

 

BOTTOM LINE:

Meanwhile, it seems too simple to change Disk Management so it does not show either A: or B: drive letters as “available” if the User wishes to change a drive letter for any reason.

 

p.s.  Sorry for ranting here;  but, this latest Windows 10 adventure has been very time-consuming, to put it mildly.

• This topic was modified 1 year, 3 months ago by SupremeLaW.

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Cybertooth

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Windows 10 version 1909 also offers drive letters A: and B: as “available” when changing a drive letter inside Disk Management:

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I’ve been using drive letters A and B for the OS partitions for my dual boot daily driver since they were made available in Windows 10 (or maybe 8/8.1?).  The booted OS always take C:.

I had a disk number shuffling issue with (I think) a Windows Update in May 2021, 21H1 Disk Management re-ordered my SSD’s.  Other than that, no other issues with using A and B.

Always create a fresh drive image before making system changes/Windows updates; you may need to start over!

We all have our own reasons for doing the things that we do with our systems; we don't need anyone's approval, and we don't all have to do the same things.

We were all once "Average Users".

Computer Specs

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SupremeLaW

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I get A thru Z (except for letters already assigned) on fully patched Windowss 10 22H2.

Just assign the driver letters you want.

Done.

 

 

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SupremeLaW

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Just a wild guess that there may be some (residual?) ‘floppy-disk’ specific code invoked (sometime/someplace) when A: or B: is nominated. The old wild-branch syndrome. There do exist USB-connected floppy disk drives. I’ve never had one, so don’t know if A: and B: are letters ‘reserved’ for assignment to this type of drive.

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SupremeLaW

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https://www.howtogeek.com/122891/what-are-the-windows-a-and-b-drives-used-for/

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SupremeLaW

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LOL!!

I know I’m not crazy;  it’s getting other Users to agree with my theory about “excess complexity” that only adds to the complexity  🙂

Did you read this in your link?

“So when I built a new computer recently with two internal drives, one for the OS and one for data, I thought, hey!, I’ll make my data drive “A”. I felt all rebellious until I discovered that Windows will not index drives lettered A or B. 🙁 “

p.s.

Q:  How many wing designs did the Wright Brothers test before they got it right?

A:  They were the Wrong Brothers several thousand times, or so I am told.

Same thing happened to Thomas Edison.

 

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Currently on Windows 10 22H2 (OS Build 19045.4046) and, since at least Windows 10 1909, have been using drive letters A: (network shared video drive) & B: (my primary external backup drive – which is in a USB 3.1 enclosure) and never encountered any problems like you describe.

SupremeLaW wrote:

we temporarily assigned drive letters to A: and B: to a WDC HDD stored inside an external USB 3.0 enclosure.

I “assume” that drive has two partitions, one for each drive letter?

It’s possible one or both of the partitions on the WD HDD has some bad sectors or something which could be causing the 100% utilization when Windows “tries” to access it.

Suggest you run Chkdsk.exe /scan to verify both partitions are clean and, if not, Chkdsk.exe /r to see if it can be and fixed.

Or possibly there’s an issue with the internal circuitry in the external enclosure itself (maybe it’s SATA ⇔ USB I/F doesn’t support multiple partitions with separate drive letters?)

BTW, the following registry location contains all the in-use drive letters.

[HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices]

If you delete the \DosDevices\A: & \DosDevices\B: entries in that section and reboot, it’ll remove any possible conflicts with the assignment of those drive letters (i.e. they’ll no longer be assigned to any drives) and you can then reassign them.

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SupremeLaW

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Update from Windows Adventure Land:

Ye ol’ wild-branch syndrome appears to be contending for the Title here.

Something woke me up at 02:30 hours this morning, so it was back to the salt mines.

On a wild guess (because I have already tried almost every other test), I DISCONNECTED one of the 2 x SFF-8087 cables which wires our Highpoint RocketRAID 2720SGL to an IcyDock enclosure.

(That enclosure has 6 x 2.5″ bays.  Very nice enclosure:  inexpensive and effective too.  Fits snugly into any available 5.25″ drive bay.)

That was a reasonable wild guess, because it was only connecting 2 x SSDs to the controller.

The other SFF-8087 cable wires that 2720SGL controller to 4 x SSDs inside that IcyDock enclosure.

With only 1 x SFF-8087 cable fully connected to 4 x SSDs, HP Z240 booted up NO PROBLEM!

OH JOY!  If at first you don’t succeed, call the Wrong Brothers.

Next test really cinched the wild-branch theory:

I re-connected the second SFF-8087 cable, but only the end which plugs into one of the two ports on that 2720SGL controller;  the 4 x SATA connectors were left dangling in open air.

VOILA!

Same nagging symptoms RE-APPEARED.

Last test:  I tried the same test with another identical SFF-8087 cable, connected to the same controller port, with 4 x SATA connectors also dangling in open air (as above).

Same nagging symptoms RE-APPEARED.

So, after all these years of superb in-service experience with Highpoint’s RocketRAID 2720SGL, I’ve convinced myself that one of the 2 SFF-8087 ports on that controller is now failing intermittently, just not all the time.

WHEW!  I feel a nap attack approaching.

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quick post-script:

HP’s original documentation for the HP Z240 tower workstation did not say very much about BIOS options for expansion slots and expansion cards.

Fortunately, HP Support Assistant makes updating the motherboard BIOS very easy.

After that update finished successfully the first time, I booted into that new BIOS and was happy to see better drop-down menu options for each PCIe expansion slot:

The factory default is PCIe Gen3 (8 GHz per lane, 130b/128b jumbo frame).

With the latest BIOS installed, the speed can now be manually changed to Gen1, Gen2 and Gen3.

PCIe 3.0 is supposed to detect and set the correct speed for each add-in card;  but, it’s nice to have the option to fix each PCIe slot’s clock speed manually.

Lastly, during normal operation the speed and number of lanes assigned to the 2720SGL controller are reported by Highpoint’s RAID Management GUI.  And, CPU-Z also reports similar data for the motherboard.

Hope this helps.

 

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Cybertooth

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