From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephan von Krawczynski Subject: Re: SSD Optimizations Date: Thu, 11 Mar 2010 18:35:06 +0100 Message-ID: <20100311183506.adce61ee.skraw@ithnet.com> References: <4B97F7CE.4030405@bobich.net> <4B9829B1.1020706@bobich.net> <20100311073853.GA26129@attic.humilis.net> <201003111159.58081.hka@qbs.com.pl> <20100311123103.34246e95.skraw@ithnet.com> <20100311143905.GA20569@attic.humilis.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: Hubert Kario , linux-btrfs@vger.kernel.org, Gordan Bobic To: sander@humilis.net Return-path: In-Reply-To: <20100311143905.GA20569@attic.humilis.net> List-ID: On Thu, 11 Mar 2010 15:39:05 +0100 Sander wrote: > Stephan von Krawczynski wrote (ao): > > Honestly I would just drop the idea of an SSD option simply because the > > vendors implement all kinds of neat strategies in their devices. So in the end > > you cannot really tell if the option does something constructive and not > > destructive in combination with a SSD controller. > > My understanding of the ssd mount option is also that the fs doens't try > to do all kinds of smart (and potential expensive) things which make > sense for rotating media to reduce seeks and the like. > > Sander Such an optimization sounds valid on first sight. But re-think closely: how does the fs really know about seeks needed during some operation? If your disk is a single plate one your seeks are completely different from multi plate. So even a simple case is more or less unpredictable. If you consider a RAID or SAN as device base it should be clear that trying to optimize for certain device types is just a fake. What does that tell you? The optimization was a pure loss of work hours in the first place. In fact if you look at this list a lot of talks going on are highly academic and have no real usage scenario. Sometimes trying to be super-smart is indeed not useful (for a fs) ... -- Regards, Stephan