I'm running ubuntu 10.10 on a Dell D400 laptop.  I'm booting and running the system from LVM volumes on a WD Scorpio Blue 2.5 drive mounted in a NexStar3 USB enclosure.For the most part, this works great.  However, after a few days or so the system will often seem to lose access to the system partition.  I'm not sure what exactly happens, and it's difficult to diagnose because I can't access the pertinent system utilities:$ mountbash: /bin/mount: Input/output error$ lsBus error$ tail /var/log/messagesbash: /usr/bin/tail: Input/output error$ cat /var/log/messagesSegmentation faultEven shutting down cannot be done cleanly:$ sudo shutdown -h nowbash: /usr/bin/sudo: Input/output error$ sudo haltbash: /usr/bin/sudo: Input/output errorThe only recovery procedure I've found is a hard reboot by holding the power button down for a few seconds.When this error state is active, the enclosure light is on steady.  Normally it blinks pretty constantly.I migrated the system files over from an internal drive.  I was not having these problems prior to the migration.  I seem to recall that they started soon afterwards.updateFollowing Gilles' suggestion to do remote logging yielded this syslog output:<6>Aug 12 01:00:25 box kernel: [229825.120148] usb 1-5: reset high speed USB device using ehci_hcd and address 2<3>Aug 12 01:00:26 box kernel: [229825.700267] usb 1-5: device not accepting address 2, error -71<3>Aug 12 01:00:26 box kernel: [229825.758145] ehci_hcd 0000:00:1d.7: port 5 reset error -110<3>Aug 12 01:00:26 box kernel: [229825.758160] hub 1-0:1.0: hub_port_status failed (err = -32)<6>Aug 12 01:00:26 box kernel: [229825.960116] usb 1-5: USB disconnect, address 2<6>Aug 12 01:00:26 box kernel: [229825.980062] sd 2:0:0:0: Device offlined - not ready after error recovery<6>Aug 12 01:00:26 box kernel: [229825.980108] sd 2:0:0:0: [sdb] Unhandled error code<6>Aug 12 01:00:26 box kernel: [229825.980112] sd 2:0:0:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK<6>Aug 12 01:00:26 box kernel: [229825.980118] sd 2:0:0:0: [sdb] CDB: Read(10): 28 00 31 b1 a0 35 00 00 20 00<3>Aug 12 01:00:26 box kernel: [229825.980132] end_request: I/O error, dev sdb, sector 833724469<3>Aug 12 01:00:26 box kernel: [229825.980167] Buffer I/O error on device dm-1, logical block 44564614<4>Aug 12 01:00:26 box kernel: [229825.980171] lost page write due to I/O error on dm-1<3>Aug 12 01:00:26 box kernel: [229825.984068] Aborting journal on device dm-4-8.<3>Aug 12 01:00:26 box kernel: [229825.984100] Buffer I/O error on device dm-4, logical block 1081344<4>Aug 12 01:00:26 box kernel: [229825.984104] lost page write due to I/O error on dm-4<3>Aug 12 01:00:26 box kernel: [229825.984113] JBD2: I/O error detected when updating journal superblock for dm-4-8.<3>Aug 12 01:00:26 box kernel: [229825.984181] Buffer I/O error on device dm-4, logical block 1675867<4>Aug 12 01:00:26 box kernel: [229825.984185] lost page write due to I/O error on dm-4<3>Aug 12 01:00:26 box kernel: [229825.984190] Buffer I/O error on device dm-4, logical block 1675868<4>Aug 12 01:00:26 box kernel: [229825.984193] lost page write due to I/O error on dm-4<3>Aug 12 01:00:26 box kernel: [229825.984200] Buffer I/O error on device dm-4, logical block 1684657<4>Aug 12 01:00:26 box kernel: [229825.984204] lost page write due to I/O error on dm-4<4>Aug 12 01:00:26 box kernel: [229825.984389] JBD2: Detected IO errors while flushing file data on dm-4-8<43>Aug 12 01:00:26 box rsyslogd: /var/log/syslog<43>Aug 12 01:00:26 box rsyslogd: /var/log/kern.log<43>Aug 12 01:00:26 box rsyslogd: /var/log/messages<2>Aug 12 01:00:26 box kernel: [229825.991754] EXT4-fs error (device dm-4): ext4_journal_start_sb: Detected aborted journal<2>Aug 12 01:00:26 box kernel: [229825.991765] EXT4-fs (dm-4): Remounting filesystem read-only<3>Aug 12 01:00:26 box kernel: [229826.136474] Buffer I/O error on device dm-1, logical block 44726233<4>Aug 12 01:00:26 box kernel: [229826.136480] lost page write due to I/O error on dm-1<3>Aug 12 01:00:26 box kernel: [229826.136487] Buffer I/O error on device dm-1, logical block 44726234<4>Aug 12 01:00:26 box kernel: [229826.136491] lost page write due to I/O error on dm-1<3>Aug 12 01:00:26 box kernel: [229826.144081] Aborting journal on device dm-1-8.<3>Aug 12 01:00:26 box kernel: [229826.144099] Buffer I/O error on device dm-1, logical block 13139968<4>Aug 12 01:00:26 box kernel: [229826.144103] lost page write due to I/O error on dm-1<3>Aug 12 01:00:26 box kernel: [229826.144110] JBD2: I/O error detected when updating journal superblock for dm-1-8.<0>Aug 12 01:00:26 box kernel: [229826.144124] journal commit I/O errorThe 10th line from the end, at 229825.991765, is where the filesystem is remounted readonly.  I scanned through the rest and didn't see anything indicating that it is fully dismounted, so it is a bit of a mystery why the system itself becomes inaccessible.In any case, the USB errors at the beginning seem to be the reason for the crash.Is this likely to be a problem with the laptop's USB controller/drivers?  Or more likely with the USB enclosure?  How can I tell?
Loss of disk access on external USB system/boot drive
usb drive;external hdd