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

Garrett Cooper yanegomi at
Fri Dec 23 20:20:20 UTC 2011

>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
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Dec 23 20:20:17 UTC 2011
>Originator:     Garrett Cooper
>Release:        10-CURRENT
FreeBSD 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r227801: Mon Nov 21 14:04:39 PST 2011     root at  amd64
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.



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