On 08/25/2011 05:23 PM, iscsi developer man wrote: > Thanks Mike, > > So what happens if we return the task set full or the busy status forever? > Does the host get an io error at a certain timeout, does the host silently > return back to the application that the operation has completed > successfully, or does it retry indefinitely? >
The info below is for the current upstream kernel. It is probably correct from about 2.6.18 - 3.*. There is a max time value that the scsi layer will retry. It depends on the command type. The algorithm is: (scsi_cmnd->allowed + 1) * scsi_cmnd->timeout. The allowed value for disk IO is 5. The timeout depends on your distro. You can see it in /sys/block/sdX/device/timeout. The kernel sets it to 30 but some distro udev version set it to 60. Users can set it to whatever makes them happy so who knows. If the command has not completed in ((scsi_cmnd->allowed + 1) * scsi_cmnd->timeout) seconds then the command is failed. In /var/log/messages you would see: "timing out command, waited X seconds", And the upper layers would get some error. The error value depends on the IO type. The block layer, dm, file systems (kernel stuff) gets -EIO. If you were doing SG IO then you would see the scsi status value you set in the SG IO's error data. -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
