Date: Fri, 5 Jul 2013 08:24:31 -0700 From: Christoph Hellwig <hch@infradead.org> To: Zoltan Arnold NAGY <zoltan.arnold.nagy@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: O_DIRECT|O_SYNC semantics? Message-ID: <20130705152431.GA21283@infradead.org> In-Reply-To: <CAGFYgbMPCcr7HmOyStLPUGkzPBHH1Xy5=pyVi1wFFwBAiehN9g@mail.gmail.com> References: <CAGFYgbMPCcr7HmOyStLPUGkzPBHH1Xy5=pyVi1wFFwBAiehN9g@mail.gmail.com>
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On Wed, Jul 03, 2013 at 09:05:40PM +0200, Zoltan Arnold NAGY wrote: > Hi, > > Could someone have a look here: > http://serverfault.com/questions/520141/please-explain-my-fio-results-is-o-synco-direct-misbehaving-on-linux > > Basically, I'm seeing wastly different results on Linux and on FreeBSD 9.1. > Either FreeBSD's not honoring O_SYNC properly, or Linux does something > wicked. > > I've been at it for a few days, without any real progress. For consumer disks using O_SYNC on Linux does make a huge difference, because it flushes the disk write cache after completion to make sure the O_SYNC gurantees that data has hit physical storage are met. It seems like FreeBSD might be missing that call.
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