Hello, I've noticed Linux seems to have issues with external USB enclosures containing drives > 2 TB. The USB mass storage driver apparently emulates a SCSI device and sends a read/write(10) for all requests where the target sector is not large enough to require the use of read(16). The issue is that both of the enclosures I was able to test with do not properly accept this read(10) command when a 3TB drive (Seagate ST3000DM) is installed. A wireshark USB trace shows the read(10) command is sent to the drive and the drive never responds. The same drive/enclosure used in Windows 7 shows that read(16) is always used to communicate with the drive and the drive works without issue with Windows 7. A few notable points: 1. The drive operates without issue when connected to an internal Sata port on my computer. 2. The enclosure operates without issue with Linux (using read(10) ) when a <2TB drive is installed. 3. I have reproduced this problem on several computers, and using several Linux kernels, including 3.7.0-rc4-next. I first reported this to the linux-usb list thinking it was a USB issue. At the request of Alan Stern I am also reporting it here. I'm not sure if I am taking the correct approach but I have written a simple patch that resolves the problem for me. In essence, the patch adds a new bit to scsi_device that indicates it should favor read/write(16) over read/write(10). sd_prep_fn is modified to check this bit, and use a 16 byte operations when a large capacity drive is in use and this bit is on. Finally, the USB storage driver's scsi glue code is modified to turn this bit on for all of its devices. Not sure if this is the correct fix, but it works for me. I'm willing to revise my fix, provide testing, and collect any debug data if requested. The patch will follow in a separate e-mail. Background info: Enclosure #1 - Vantec NexStar CX USB 3.0/2.0 idVendor 0x174c ASMedia Technology Inc. idProduct 0x55aa bcdDevice 1.00 iManufacturer 2 ASMedia iProduct 3 AS2105 Enclosure #2 - Rosewill idVendor 0x152d JMicron Technology Corp. / JMicron USA Technology Corp. idProduct 0x2338 JM20337 Hi-Speed USB to SATA & PATA Combo Bridge bcdDevice 1.00 Relevant posts to linux-usb: http://thread.gmane.org/gmane.linux.usb.general/74275 http://thread.gmane.org/gmane.linux.usb.general/74364 -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
