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Re: [zfs-discuss] 15 minute fdsync problem and ZFS: Solved

Subject: Re: [zfs-discuss] 15 minute fdsync problem and ZFS: Solved
From: Bill Sommerfeld
Date: Wed, 21 Jun 2006 15:03:12 -0400
On Wed, 2006-06-21 at 14:15, Neil Perrin wrote:
> Of course we would need to stress the dangers of setting 'deferred'.
> What do you guys think?

I can think of a use case for "deferred": improving the efficiency of a
large mega-"transaction"/batch job such as a nightly build.

You create an initially empty or cloned dedicated filesystem for the
build, and start it off, and won't look inside until it completes.  If
the build machine crashes in the middle of the build you're going to
nuke it all and start over because that's lower risk than assuming you
can pick up where it left off.

now, it happens that a bunch of tools used during a build invoke fsync. 
But in the context of a full nightly build that effort is wasted.  All
you need is one big "sync everything" at the very end, either by using a
command like sync or lockfs -f,  or as a side effect of reverting from
sync=deferred to sync=standard.

                                        - Bill

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