zfsonlinux/zfs — pull request #2387 by ryao (2014-06-11 15:32:25+00:00)
Title: Introduce module parameters for handling IO timeouts

The low level formatting of magnetic drives contains ECC that permits
error correction. When a drive reads a bad sector, it will keep trying
to read it is reached in the hope that a different read attempt will
allow the ECC to reconstruct the bad data until an internal time out
occurs. This is useful on filesystems that cannot recover from drive
errors. However, it is unnecessary as ZFS can easily self heal when
errors occur.

We introduce a tunable called zfs_vdev_disk_timeout_ms that allows us to
tell the block layer to send the errors to ZFS earlier than normal. We
also introduce zfs_vdev_disk_timeout_ticks, which is the maximum number
of consecutive timeouts before a disk is marked as being bad.

Signed-off-by: Richard Yao