USB MSD with multiple partitions

[egovind]

Hi,

I would like to create a USB MSD device with 2 partitions. What is the right way to go about it?

1. Do I just mount as a LUN = 1 device and then allow the host operating system to partition the media disk appropriately? I am aware that this method has a problem in Windows 7, that it only mounts one partition for removable disks

2. Do I set LUN = 2 and setup the firmware so that LUN1 LBA[0,MAX] are mapped to [LBA 0, MEDIA_MAX_LBA/2] on the media and LUN2 LBA[0,MAX] are mapped to [MEDIA_MAX_LBA/2, MEDIA_MAX_LBA ] ? In this case I presume the OS would see two disks corresponding to each LUN and would install an MBR on each of them?

The "media" in my case is an SD Card.

Govind

[Bret]

I think you've already answered your own question.  If you want it to work with Windows and don't want to write a custom driver, you'll need to do option 2.

Also, the problem of only mounting one partition I don't think is limited to Windows 7.  I'm not 100% positive, but I think it started in Vista and is a "feature" in all versions of Windows since Vista.

[egovind]

Great! Thanks a lot for the feedback!