"Mavericks 10.9 (13A603) doesn't fully support 17" 2010 MacBook Pro ExpressCard Slot.
  FirmTek testing has discovered if the release version of Mac OS X 10.9 (13A603) is installed on a 17" 2010 MacBook Pro model MacBookPro6,1, and an eSATA card is inserted into the ExpressCard slot - no hard drives will mount using the card. The proper drivers can be installed but with this particular model the hard drives will not mount or show up in Disk Utility with OS X 10.9. FirmTek suggests 2010 17" MacBook Pro users that rely on the ExpressCard slot should not upgrade to OS X 10.9 until this issue is resolved. If anyone observes a different result please let us know.

This bug does NOT apply to the 2009 or 2011 17" MacBook Pro models which fully support all FirmTek eSATA ExpressCards with Mac OS X 10.9. If a customer has an ExpressCard issue with the 2011 or 2009 MBP model, reinstalling the proper driver will usually correct the issue and the eSATA ExpressCard will then mount the drives.
  (Often a driver reinstall after a major OS X update was required for SI3132 based eSATA cards in the past. Even the OS X 10.6.x installer removed SI3132 card drivers IIRC (into an incompat. software folder), although simply installing the drivers again usually worked as mentioned in posts here back then. I saw that with both my PCIe and Expresscard eSATA cards (Silicon Image 3132 based). One reason why I replaced the PCIe SI3132 card with a natively supported NewerTech 6G eSATA card, as I didn't need PM support.)

As the 2009 and 2011 MacBook Pro ExpressCard slots work as expected with 10.9, this seems to suggest the 10.9 installer may need an update to fully support the 2010 MBP ExpressCard hardware. I hope this information is helpful,
Michael
FirmTek, LLC"

Thanks. And below are earlier (and later) reports from readers on the same problem. (Although not mentioned in reports below, I assume any card driver reinstalls were tried in 10.9 to no avail - Firmtek said (above) that didn't help in the case of the MacBook Pro 6,1 model.)

"Mavericks = ExpressCard34 Support Gone.
I have a MacBook Pro 17" (MacBookPro6,1) with ExpressCard 34 Slot. I have it set up with multiple partitions for BootCamp Win7, OS X 10.6.8 (main working systems because of need for Rosetta) and a spare partition that I install different OS X Variants on for testing as I do software development.

I installed Mavericks (OS X 10.9) over top of Mountain Lion (10.8.x). I ran updaters on ML, backed it up to a .dmg and checked the partitions with Disk Utilities before doing the update too.

Under Mavericks, none of my PC 34 Express Cards are recognized. In fact when I check "About this Mac" using System Profiler, it doesn't even indicate I have a PCI (Expresscard) slot. None of the PC (Expresscard) Cards show up on the menu bar (like they did before) to eject either.

So my eSata, Generic USB 3 and CalDigit USB 3 PCExpress card are toast under 10.9. They were recognized under Mountain Lion and earlier and are still recognized under 10.6.8 - my main system.

Good thing this is a "Free Update", cause if I had paid money for this sort of "innovation", I would be even more severely PO'd. One more step to dumbing down your Mac until it has parity with your iPhone.
-Milton"

Thanks for the note Milton. (See below for his later reply.) I have an Early 2009 17in MacBook Pro (rarely used) but never updated it beyond 10.6.8. Still the OS version I use most and prefer. (And always beware a major "dot zero" release.) I used that MBP with some eSATA ExpressCards several years ago. (Both natively supported and SI3132 eSATA cards that required drivers. The natively supported card (single port JMB36x based) had some intermittent data corruption on file copies, noted on the old Expresscard reports page.)

And another mail on the subject from Nov 1st AM:

"Mavericks on a 2010 17" MBP with ExpressCard 34 slot
I have a 2010 17-inch MacBook Pro with ExpressCard 34 slot.
Neither of my eSATA or CalDigit USB 3.0 cards work after upgrading to OS X 10.9/Mavericks.
Both worked perfectly under Mountain Lion.
-Ben K."

Thanks Ben. Hopefully Apple will fix this in the next update/build (10.9.1?).

(Update) I had written both Milton and Ben to confirm they'd tried driver reinstalls (won't help per Firmtek but just wanted to verify). Here's their later replies:

"Re: Mavericks on a 2010 17" MBP with ExpressCard 34 slot
Yes I tried all manner of reinstalls and hacks... does nothing for the 2010 MacBookPro issue.

The problem isn't that the drivers don't work per se - more that the PCIe bus isn't recognised at all under the system. Under the PCI section of the system profiler I see this:

"This computer doesn't contain any PCI cards. If you installed PCI cards, make sure they're properly installed."
...and so the drivers don't load even though they do show up as extensions.

FYI my MBP model is: MacBook Pro 17-inch, Mid 2010 (MacBookPro6,1), Intel Core i7 2.66 GHz. Boot ROM MBP61.0057.B0F, SMC V1.57f18. Obviously with an ExpressCard 34 slot. The slot works for power and with a card in the slot it will power a usb device but no data or communication with it.
Best, Ben K.
Designer / Director / Editor
Television | Film | Multimedia"

And here's Milton's reply (Nov 1st):

"(Follow-up on 2010 MacBook Pro Expresscards not recognized.)
I contacted CalDigit as their USB 3 card is DOA in Mavericks.
According to them, Apple "forgot" to add in the low level PCI Express Card code / drivers. So there is no PC34 (express) card support and therefore, nothing will work - regardless if we have or don't have drivers for the cards. That does match what I have seen - the Apple Profiler says there is no PC Card support for this model.

A hand full of people have posted similar results (all 2010 MBP 17" model) on the Apple Forums too with a variety of Cards (SSD, FireWire, USB, e-Sata) - see
Mavericks does not recognize ExpressCard. (with a later post from a 2008 MBP owner.)
I filed a Bug Report with Apple this afternoon too, so maybe this will be fixed in the next update.
-Milton"

I noticed a post from "cascag" there says he finally got his JMicron jmb363 eSATA card to work (with some 3rd party drivers/mods). [Later posts in that thread have other more recent notes and tips.] I remember some Jmicron JMB36x based cards were natively supported in the past. I have a single port version (JMB360 I think) that worked w/o drivers in my 2009 MBP (OS X 10.5/10.6) but as I said several years ago (when 10.6.2 was current), I stopped using it after checksum tests on file copies showed intermittent verify failures - sometimes 1 in 10, sometimes more. (Added a red/sticky on that to the expresscard page.) Not everyone noticed this (many didn't test/check for it) but some others did with the same card (single-port model/chipset). An owner back then with the 2-port JMB362 card said he had no such problems. (I still have that single port card here but no plans to update the 2009 17in MBP from 10.6.8 to anything later, especially not Mavericks at this point - a dot zero release.)
  

"External Drives for Mac Experiencing Data Loss with Maverick OS -- UPDATED FOR NOVEMBER 6th, 2013

--- Updated November 6, 2013 ---
On October 30th, 2013 Western Digital informed registered customers of affected products via E-mail regarding reports of Western Digital and other external HDD products experiencing data loss when updating to OS X Mavericks (10.9). Our investigation to date has found that for a small percentage of customers that have the WD Drive Manager, WD Raid Manager and/or WD SmartWare software applications installed on their Mac, there can be cases of a repartition and reformat of their Direct Attached Storage (DAS) devices without customer acknowledgement which can result in data loss.

WD has been tracking this issue closely through our WD Forum and through our Technical Support hotline and the occurrence rate of this event has been very low. A specific set of conditions and timing sequences between the OS and the WD software utilities has to occur to cause this issue. Should this event occur, the data on the product can likely be recovered with a third party software utility if the customer stops using the device immediately after the OS X Mavericks (10.9) upgrade. WD will be issuing updated versions of these software applications that resolve this issue.

WD strongly urges our customers to uninstall these software applications before updating to OS X Mavericks (10.9), or delay upgrading until we provide an update to the applications. If you have already upgraded to Mavericks, WD recommends that you remove these applications and restart your computer. If you have already upgraded to Mavericks and are experiencing difficulty in accessing your external hard drive, please do not save anything to the drive, disconnect the drive from your computer, and contact Western Digital Customer Service at https://support.wdc.com/contact/.

--- Updated November 5, 2013 ---
There are reports of Western Digital and other external HDD products experiencing data loss when updating to Apple's OS X Mavericks (10.9). Western Digital is urgently investigating these reports and the possible connection to the WD Drive Manager, WD Raid Manager and WD SmartWare software applications.

Until the issue is understood and the cause identified, WD strongly urges our customers to uninstall these software applications on their systems before updating to OS X Mavericks (10.9), or delay upgrading. If you have already upgraded to Mavericks, WD recommends that you remove these applications and restart your computer. WD has removed these software applications from our web site solely as a precaution as we investigate this issue.

If you have already upgraded to Mavericks and are experiencing difficulty in accessing your external hard drive, please do not save anything to the drive, disconnect the drive from your computer, and contact Western Digital Customer Service at http://support.wdc.com/country/ for further assistance.

You can now download the WD Software Uninstaller. This utility will remove Mac WD SmartWare and WD Drive Manager software. You can find the uninstaller under any of the Mac Drive Downloads sections such as the My Book Studio below.
https://support.wdc.com/product/download.asp?groupid=124&sid=214&lang=en"
(Scroll down that page to see the Mac "WD Software Uninstaller" Download button. The Uninstaller is listed as supporting Mac OS X 10.9, 10.8, 10.7 and 10.6.
Update: As of Nov 25th, 2013 the WD Uninstaller is no longer at that page.)

There were also threads in WD's Forums on OS X 10.9 problems. And the Apple forum thread on Mavericks corrupts external hard drives has grown to 12 pages as of Oct. 31st and includes many WD owner posts and some from users of other brands. Included in posts there are some WD software removal notes and suggestions on data recovery software. (I don't use WD drives and would never install typical retail drive addon SW so I've not read every post on this but where is WD's info on removal of their software? Or is an uninstall option included in the installer? (Update: they finally added a link in Nov 5th update above.)
  

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