ZFS on a notebook/512M settings

[Pawel Jakub Dawidek]

On Wed, Jul 25, 2007 at 05:20:35PM -0500, Craig Boston wrote:
> I've seen recommendations on the BSD lists to use zil_disable to avoid
> low-memory deadlocks (which I've not yet encountered).  I've also seen
> dire warnings on the OpenSolaris lists about possible data corruption if
> you disable the ZIL, so I'm unsure about that one.  For now I'm erring
> on the side of caution and leaving it enabled until it causes me
> problems.

Let me explain what disabling ZIL really means. Once ZIL is disabled,
fsync(2) is a no-op, ie. calling fsync(2) on a descriptor doesn't mean
your data would be safely stored on disk at the time function returns.
There is no data corruption for local use, only this fsync(2) problem.

"Data corruption" can happen from NFS client point of view, when your
ZFS file system is exported over NFS and your NFS server crashes.

You can read more details here:

	http://blogs.sun.com/roch/entry/nfs_and_zfs_a_fine

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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