docs/163576: zfs(8) sync property not noted in the manpage

[Garrett Cooper]

>Number:         163576
>Category:       docs
>Synopsis:       zfs(8) sync property not noted in the manpage
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Dec 23 20:20:17 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Garrett Cooper
>Release:        10-CURRENT
>Organization:
n/a
>Environment:
FreeBSD streetfighter.ixsystems.com 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r227801: Mon Nov 21 14:04:39 PST 2011     root at streetfighter.ixsystems.com:/usr/obj/usr/src/sys/STREETFIGHTER  amd64
>Description:
The sync property isn't discussed in the zfs(8) manpage.

The sync property allows administrators to turn off write synchronization at the "filesystem" level (in reality the ZIL level according to /sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c), which might improve performance in some scenarios.

Just like setting checksum=off though, it should be highly discouraged option to tweak because with standard setups and with some disk technologies (*ATA and some big HDD vendors, I'm looking at you ;)..), this could result in catastrophic data loss in the event where enough drives become unavailable, there's a system (software/hardware) failure, or power outage.
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: