dmesg outuput: 

scsi 2:0:0:0: Direct-Access     SONY     NWWM MEM AAD2    1.00 PQ: 0 ANSI: 0 CCS
sd 2:0:0:0: Attached scsi removable disk sda
sd 2:0:0:0: Attached scsi generic sg0 type 0
usb-storage: device scan complete
SCSI device sda: 496513 2048-byte hdwr sectors (1017 MB)
sda: Write Protect is off
sda: Mode Sense: 00 6a 00 00
sda: assuming drive cache: write through
SCSI device sda: 496513 2048-byte hdwr sectors (1017 MB)
sda: Write Protect is off
sda: Mode Sense: 00 6a 00 00
sda: assuming drive cache: write through
 sda: sda1
usb 1-8: USB disconnect, address 2
sd 2:0:0:0: SCSI error: return code = 0x00010000
end_request: I/O error, dev sda, sector 1726144
sd 2:0:0:0: SCSI error: return code = 0x00010000
end_request: I/O error, dev sda, sector 1726384
Buffer I/O error on device sda1, logical block 123
lost page write due to I/O error on sda1
usb 1-8: new high speed USB device using ehci_hcd and address 3
usb 1-8: configuration #1 chosen from 1 choice
scsi3 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 3
usb-storage: waiting for device to settle before scanning
scsi 3:0:0:0: Direct-Access     SONY     NWWM MEM AAD2    1.00 PQ: 0 ANSI: 0 CCS
sd 3:0:0:0: Attached scsi removable disk sdb
sd 3:0:0:0: Attached scsi generic sg0 type 0
usb-storage: device scan complete
usb 1-8: USB disconnect, address 3
usb 1-8: new high speed USB device using ehci_hcd and address 4
usb 1-8: configuration #1 chosen from 1 choice
scsi4 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 4
usb-storage: waiting for device to settle before scanning
scsi 4:0:0:0: Direct-Access     SONY     NWWM MEM AAD2    1.00 PQ: 0 ANSI: 0 CCS
sd 4:0:0:0: Attached scsi removable disk sdb
sd 4:0:0:0: Attached scsi generic sg0 type 0
usb-storage: device scan complete

syslog:
ar 22 20:24:32 lightstar kernel: sda: assuming drive cache: write through
Mar 22 20:24:32 lightstar kernel: sda: assuming drive cache: write through
Mar 22 20:24:54 lightstar kernel: end_request: I/O error, dev sda, sector 1726144
Mar 22 20:24:54 lightstar kernel: end_request: I/O error, dev sda, sector 1726384
Mar 22 20:24:54 lightstar kernel: Buffer I/O error on device sda1, logical block 123
Mar 22 20:24:54 lightstar kernel: lost page write due to I/O error on sda1