MFC r348577: MFV r348576: 9963 Seperate tunable for disabling ZIL vdev flush
illumos/illumos-gate@f8fdf6812567ce1a3b76a6bee2ee3f04bd3fcaca
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Prakash Surya <prakash.surya@delphix.com>