I have a USB disk enclosure with four Seagate ST31000340AS drives in it. Each drive has 1953525168 sectors, so that's 7814100672 sectors total for the array, or 3.64 TB. There is a mode switch on the back of the array; according to the manual, when the switch is in position A, it will present a single large volume even when over 2 TB, which supposedly works with 64-bit Windows, or, with the switch in position B, it will split itself into two volumes under 2 TB if necessary. Now, with a stock 2.6.30 kernel on sparc64, here's what happens when I attach the enclosure with the mode switch in position B: usb 3-3.6: new high speed USB device using ehci_hcd and address 10 usb 3-3.6: New USB device found, idVendor=0dc4, idProduct=0004 usb 3-3.6: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 3-3.6: Product: MGB Quadro usb 3-3.6: Manufacturer: GalaxyMetalGear usb 3-3.6: SerialNumber: 540323 usb 3-3.6: configuration #1 chosen from 1 choice scsi4 : SCSI emulation for USB Mass Storage devices scsi 4:0:0:0: Direct-Access External Disk 0 1.15 PQ: 0 ANSI: 4 sd 4:0:0:0: [sda] 3907050336 512-byte hardware sectors: (2.00 TB/1.81 TiB) sd 4:0:0:0: [sda] Write Protect is off sd 4:0:0:0: [sda] Mode Sense: 10 00 00 00 sd 4:0:0:0: [sda] Assuming drive cache: write through sd 4:0:0:1: [sdb] 3907050336 512-byte hardware sectors: (2.00 TB/1.81 TiB) sd 4:0:0:1: [sdb] Write Protect is off sd 4:0:0:1: [sdb] Mode Sense: 10 00 00 00 sd 4:0:0:1: [sdb] Assuming drive cache: write through Okay, that looks good. Two LUNs of 3907050336 sectors each exactly account for all the disk capacity I have installed. I can run LVM over them and get a single 3.6 TB volume. The trouble starts when I try to put the mode switch in position A: usb 3-3.6: new high speed USB device using ehci_hcd and address 11 usb 3-3.6: New USB device found, idVendor=0dc4, idProduct=0004 usb 3-3.6: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 3-3.6: Product: MGB Quadro usb 3-3.6: Manufacturer: GalaxyMetalGear usb 3-3.6: SerialNumber: 540323 usb 3-3.6: configuration #1 chosen from 1 choice scsi5 : SCSI emulation for USB Mass Storage devices scsi 5:0:0:0: Direct-Access External Disk 0 1.15 PQ: 0 ANSI: 4 sd 5:0:0:0: [sda] 3519133184 512-byte hardware sectors: (1.80 TB/1.63 TiB) sd 5:0:0:0: [sda] Write Protect is off sd 5:0:0:0: [sda] Mode Sense: 10 00 00 00 sd 5:0:0:0: [sda] Assuming drive cache: write through Now, it seems noteworthy that 3519133184 is just 7814100672 & 0xffffff00, but I'm not sure exactly what it means. Noticing that the code in sd_read_capacity() of drivers/scsi/sd.c tries READ CAPACITY(10) first, and then uses READ CAPACITY(16) only if that returns 0xffffffff, I tried patching it to always try READ CAPACITY(16) first on this device. That led to this (with verbose USB mass storage messages enabled): usb-storage: Command (unknown command) (16 bytes) usb-storage: 9e 10 00 00 00 00 00 00 00 00 00 00 00 20 00 00 usb-storage: Bulk Command S 0x43425355 T 0x3 L 32 F 128 Trg 0 LUN 0 CL 16 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 32 bytes, 1 entries usb-storage: Status code -32; transferred 0/32 usb-storage: clearing endpoint halt for pipe 0xc0008380 usb-storage: usb_stor_control_msg: rq=01 rqtype=02 value=0000 index=81 len=0 usb-storage: usb_stor_clear_halt: result = 0 usb-storage: Bulk data transfer result 0x2 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x3 R 32 Stat 0x1 usb-storage: -- transport indicates command failure usb-storage: -- unexpectedly short transfer usb-storage: Issuing auto-REQUEST_SENSE usb-storage: Bulk Command S 0x43425355 T 0x4 L 18 F 128 Trg 0 LUN 0 CL 6 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 18 bytes, 1 entries usb-storage: Status code 0; transferred 18/18 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x4 R 0 Stat 0x0 usb-storage: -- Result from auto-sense is 0 usb-storage: -- code: 0x70, key: 0x5, ASC: 0x20, ASCQ: 0x0 usb-storage: Illegal Request: Invalid command operation code usb-storage: scsi cmd done, result=0x2 So, as far as I can tell, this means that this device doesn't support READ CAPACITY(16). Does anyone out there know anything else it might be expecting? I have no access to a Windows machine, so I can't whether it really does work with 64-bit Windows. Is this hardware just buggy over 2 TB, or is there some other mechanism besides the 0xffffffff from READ CAPACITY(10), then READ CAPACITY(16) that it could be using to indicate its capacity? -- Andrea Shepard
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