USB flash drive defined as boot device but not visible by the boot driver.

Question

I have installed Mountain Lion (10.8.2) over Lion a few days ago. In the follow-up operations, I tried to create a USB flash drive recovery device, using methods widely advertised over the web. I first tried this with an 8 GB "Kingston DT 101 G2" device. The creation of the device either manually through the use of the Disk Utility or using a small utility called Lion DiskMaker 2.0.2 worked OK.
However, after setting the resulting device as the boot device through "System Preference", it never booted on it, but instead on the normal system disk. Conversely, when booting with the option key depressed, I could only see as option the normal system disk or its recovery partition, but never the USB flash drive, although it was present.
After numerous tests, through the so-called "trial and error" method, I eventually found out that I obtained perfectly bootable USB devices with either a generic device seen as "USB 2 USB Flash Drive" by the disk utility, or with a "Kingston Data Traveler G3" USB flash drive (both being 8 GB devices).
Now, I can understand that, for whatever reason, some USB devices, although formatted as boot devices, will not be seen by the boot driver. But, in such a case, it is a serious issue that "System Preference" accepts to set them as boot devices. I would suggest that "System Preference" tests whether the boot driver is able to see them and, if not, issues an error message instead of accepting them as boot device.
I also have an unrelated side question: when restoring a disk through the Disk Utility, is the resulting new volume defragmented and compacted by the process or not?

Answer 1

I can only tell you that some USB flash drives don't work as expected on Macs, and I don't believe it is specifically related to the product since they often work for others. I have five flash drives from a particular manufacturer that when plugged into one of my computers are not recognized, yet they are on all my other computers. I have six or seven older ones from the same manufacturer, same model, that work fine on all my computers. I have two Kingston Travelers that would not work as a bootable device on any of my computers. Many other users here have had issues with San Disk flash drives.
I don't know if this helps any, but at least you can know that you aren't alone.
One thing I can suggest is when you prepare a new flash drive that you go through this process:
1. Open Disk Utility in your Utilities folder.
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Security button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.
This may fix boot problems with new flash drives because they are often prepared by the manufacturer with NTFS. To fully clear the drive you must both partition and format the device. Writing zeros has in some cases helped make a drive bootable when at first it was not.