Date: Wed, 17 Aug 2016 17:49:44 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Nathan Whitehorn <nwhitehorn@freebsd.org> Cc: Dag-Erling =?utf-8?B?U23DuHJncmF2?= <des@des.no>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r304142 - head/usr.sbin/bsdinstall/partedit Message-ID: <20160817144944.GM22212@zxy.spb.ru> In-Reply-To: <581c856c-826b-529e-c9c6-a397fb679708@freebsd.org> References: <201608150930.u7F9UL1V069576@repo.freebsd.org> <e3454e8e-5d98-5bec-21de-8ea0db2b9b08@freebsd.org> <861t1n6749.fsf@desk.des.no> <581c856c-826b-529e-c9c6-a397fb679708@freebsd.org>
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On Wed, Aug 17, 2016 at 07:36:00AM -0700, Nathan Whitehorn wrote: > > Your contention that the installer does not make policy decisions is > > equally spurious. The installer makes many policy decisions, including > > the disk layout, the size of the swap partition, the name of the pool, > > the use of boot environments (which I dislike but am not allowed to > > override), the number of filesets and their mountpoints (which I also > > dislike and am not allowed to override either), etc. The Unix > > philosophy is to push such decisions up the stack, not down. The > > decision to align partitions on 4096-byte boundaries because we're not > > sure of the correct number but know for a fact that using a smaller > > number can have a huge impact on performance is the installer's to make. > > Those are all things that the operating system does not have defaults > for: there are no tools like, say, gpart or newfs that layout disks in > any even vaguely automated way, and so no tools that would ever have > defaults for, say, the size of a swap partition except for the > installer. As such, the defaults are quite properly in the installer. > This is quite different: there are many tools that care about disk > alignment (say, gpart) and, by default, use the GEOM stripesize. The > installer is, after this patch, overriding what was meant to be a > system-wide default. > > My concern is that pushing this into the installer means that newfs, > zfs, gpart, etc., which all look at the GEOM stripesize for preferred > alignment, will still have suboptimal behavior on systems affected by > your patch. If we identified which drivers are reporting the wrong > alignment, we could fix the whole system at a go by changing it there. > As it is, we now have inconsistent default behavior for partitions > between tools (the installer and sade will now use a different alignment > than gpart on whatever systems you were trying to fix here) and between > pre- and post-installation environments. In long term, prefered aligment is forsing 4k (or may be more): install system on 512b [mirror] disk aligment now may be need required replace disk to 4k aligment. For more flexsible in future now best chois is 4k or more.
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