Date: Fri, 16 Oct 2015 16:19:40 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Warner Losh <imp@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r289405 - head/sys/ufs/ffs Message-ID: <20151016131940.GE42243@zxy.spb.ru> In-Reply-To: <201510160306.t9G3622O049128@repo.freebsd.org> References: <201510160306.t9G3622O049128@repo.freebsd.org>
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On Fri, Oct 16, 2015 at 03:06:02AM +0000, Warner Losh wrote: > Author: imp > Date: Fri Oct 16 03:06:02 2015 > New Revision: 289405 > URL: https://svnweb.freebsd.org/changeset/base/289405 > > Log: > Do not relocate extents to make them contiguous if the underlying drive can do > deletions. Ability to do deletions is a strong indication that this > optimization will not help performance. It will only generate extra write > traffic. These devices are typically flash based and have a limited number of > write cycles. In addition, making the file contiguous in LBA space doesn't > improve the access times from flash devices because they have no seek time. In reality, flash devices have seek time, about 0.1ms. Many flash devices can do 8 simultaneously "seek" (I think NVMe can do more).
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