Why do I see I/O errors on a RHEL system using devices from an active/passive storage array?

Solution Verified - Updated -


  • I see I/O errors in my system logs from some of the devices on my storage array / SAN
  • When I run LVM commands, I get I/O errors against some of the devices from my storage array
  • Error message "end_request: I/O error, dev sdb, sector 0" found in messages file
  • Error message "Buffer I/O error on device sdc, logical block 0" found in messages file
  • Additional messages about "sense key: Not Ready" may also be found:

        kernel: end_request: I/O error, dev sdc, sector 0
        kernel: sd 0:0:0:3: Device not ready: <6>: Current: sense key: Not Ready
        kernel:     Add. Sense: Logical unit not ready, manual intervention required
  • These end_request: I/O error messages are also logged on system console during boot process

  • On system with multipath configured, running LVM commands sometime hang or take long time and shows following error messages:
/dev/sde: read failed after 0 of 4096 at 0: Input/output error


  • Red Hat Enterprise Linux(RHEL) 4
  • Red Hat Enterprise Linux(RHEL) 5
  • Red Hat Enterprise Linux(RHEL) 6
  • Storage array operating in active/passive mode (see root cause for details)

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