Date: Fri, 19 Aug 2016 11:57:23 -0400 From: Allan Jude <allanjude@freebsd.org> To: Warner Losh <imp@bsdimp.com>, =?UTF-8?Q?Dag-Erling_Sm=c3=b8rgrav?= <des@des.no> Cc: Nathan Whitehorn <nwhitehorn@freebsd.org>, src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r304142 - head/usr.sbin/bsdinstall/partedit Message-ID: <c4aa117e-ba9d-92d5-ff65-e18a19fe5e83@freebsd.org> In-Reply-To: <CANCZdfpggS65JcfTo7bFn_4dutcJ%2Bc%2BQ%2BzbXJwORO2kjan%2BhWA@mail.gmail.com> 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> <86wpjf4eun.fsf@desk.des.no> <8cb3fa1a-50cb-e238-d006-b98a628d446d@freebsd.org> <86k2ff4cxs.fsf@desk.des.no> <b96c3f91-faaa-2552-b4da-2d0d382461af@freebsd.org> <86fuq24d8s.fsf@desk.des.no> <2f9fb04c-7ec4-be40-8fcb-0cf74bb56859@freebsd.org> <CANCZdfrGhFTR5sbKRiehXQhhexX=KfW920NJJg0Je=yigqEyEA@mail.gmail.com> <86inuxckve.fsf@desk.des.no> <CANCZdfpggS65JcfTo7bFn_4dutcJ%2Bc%2BQ%2BzbXJwORO2kjan%2BhWA@mail.gmail.com>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --HBoKUtE0wg8OgvF8HaIeneDahTDhXpNSt Content-Type: multipart/mixed; boundary="jAP4CfVQqcvQPCnoNDJvL0XrEI6hqrdEk" From: Allan Jude <allanjude@freebsd.org> To: Warner Losh <imp@bsdimp.com>, =?UTF-8?Q?Dag-Erling_Sm=c3=b8rgrav?= <des@des.no> Cc: Nathan Whitehorn <nwhitehorn@freebsd.org>, src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Message-ID: <c4aa117e-ba9d-92d5-ff65-e18a19fe5e83@freebsd.org> Subject: Re: svn commit: r304142 - head/usr.sbin/bsdinstall/partedit 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> <86wpjf4eun.fsf@desk.des.no> <8cb3fa1a-50cb-e238-d006-b98a628d446d@freebsd.org> <86k2ff4cxs.fsf@desk.des.no> <b96c3f91-faaa-2552-b4da-2d0d382461af@freebsd.org> <86fuq24d8s.fsf@desk.des.no> <2f9fb04c-7ec4-be40-8fcb-0cf74bb56859@freebsd.org> <CANCZdfrGhFTR5sbKRiehXQhhexX=KfW920NJJg0Je=yigqEyEA@mail.gmail.com> <86inuxckve.fsf@desk.des.no> <CANCZdfpggS65JcfTo7bFn_4dutcJ+c+Q+zbXJwORO2kjan+hWA@mail.gmail.com> In-Reply-To: <CANCZdfpggS65JcfTo7bFn_4dutcJ+c+Q+zbXJwORO2kjan+hWA@mail.gmail.com> --jAP4CfVQqcvQPCnoNDJvL0XrEI6hqrdEk Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 2016-08-19 10:13, Warner Losh wrote: > On Fri, Aug 19, 2016 at 12:51 AM, Dag-Erling Sm=C3=B8rgrav <des@des.no>= wrote: >> Warner Losh <imp@bsdimp.com> writes: >>> Allan Jude <allanjude@freebsd.org> writes: >>>> Which makes more sense: >>>> >>>> A) If stripesize =3D=3D 0, use some sane value like 4096 >>> >>> I don't like this. >>> >>>> B) Some other combination that uses the reported stripe size, unless= it >>>> is 0, in which case it uses 4096 (or some other value controlled by = a >>>> different new sysctl) >>> >>> Don't like this so much. >>> >>>> C) create kern.geom.min_stripe_size with a default of 512, but users= can >>>> set 4096 if they use only 4k devices. (doesn't really solve the prob= lem >>>> for the installer) >>> >>> Default it to 4k, and allow users to set it to 512. If the drive >>> reports < this value >>> report this value instead. >> >> I don't like either option. Option D (which I don't like either, but >> which should at least work in most cases) is a sysctl that specifies a= >> minimum factor, and set the reported stripe size to the least common >> multiple of that number and the actual stripe or sector size. This is= >> what my bsdinstall patch does. However, I think that pushing this dow= n >> to a layer where it will affect all applications is a terrible idea, >> because we have no way of knowing what will break[*], and it can >> seriously mislead users and hinder troubleshooting - especially if it = is >> enabled by default rather than only when necessary. >=20 > I took a look into the implications of doing a 4k stripesize 'automatic= ally' > this morning. I found a few places in g_part where it would actively > hurt when coupled with gpart's insistence on aligning things. So I > now think it's a bad idea. This will make it harder for FreeBSD to > generate arbitrary disk layouts. And I'm not too sure about what > things like gstripe would report as a result and if this would actually= > interfere if you had a large, but not power of two stripe size. >=20 >> I don't think it's a good idea to enforce stripe alignment everywhere,= >> either. It works for partitions because they are very large relative = to >> the stripe size, and at worst we will waste a few millionths of the di= sk >> on inter-partition gaps, which should only occur between the partition= >> table and the boot partition, and possibly, if the stripe size is very= >> large, between the boot partition and the swap partition. But forcing= >> filesystems to respect the stripe size will lead to no end of trouble,= >> because RAID volumes can have stripe sizes of 16 kB or more. I think = it >> is important to align partitions during installation because of the hu= ge >> performance impact of misaligned partitions on AF disks, but despite >> what Nathan claims, I never advocated applying the same logic >> everywhere. >=20 > Yea, having poked at it for just a little while, I agree. The installer= is the > right place to make sure we don't cross-thread the 4k sectors. Stripe s= ize > means too many other things to have it be useful in that context. >=20 > Warner >=20 Maybe instead we just change gpart to default to 4k alignment, but users can always override with -a 512 or some other value? Then the installer behaves the same as a user typing 'gpart', but we don't mess with the entire geom layer? --=20 Allan Jude --jAP4CfVQqcvQPCnoNDJvL0XrEI6hqrdEk-- --HBoKUtE0wg8OgvF8HaIeneDahTDhXpNSt Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (MingW32) iQIcBAEBAgAGBQJXtyxkAAoJEBmVNT4SmAt+aHsQALZH84SBlTJAX36cnNuq8/vZ Iy/NGS364jYsz/rwT1mTLqaB5e+Iiu9ZCF8dkDocAr9X4EqfuxWKuI0pZoPzxJtI zjgxwuWMU21UoSBffpncK3R/iHw1faz2Xq4lV+IKKyS22U9XJGmr3uC+k6Lu3J2m ja7uFKdVaBSNH0FG4+HygUGyRtL4vUZiAa9whe/u/hgxVv/JQCZTwQ86DTSzjEYz volBGOb1ooiVPBDqm/WP53SJCL/5nSUthMxn2NdK1scD7LlYNKXAS6dC1Lgf942c KSZ9c+noIppz/OQovkmGzCepRKvcWSHm+NIcEVXCrFj8oaVH8ys8/i9DMPhDbdD+ CeIpOTYB+yiGFCiWp07y5yTLtOAcH1873zoy/yB6iNadSuCVgKDvqO3dEe1cEJcL O7cl2lOoWJwYHRbfZuPvATc4X91suhO0KQfZJ9+GeXpUIrvl/TCXMFYrRfM+8nPK hK4bdvLVrmSOS1eiU0cZIIvrxgJ1mjtHARW9sBBLVowN+gJ1lQ8U+u93PFfncJ7K YQ+m0/s8AGg406uud68H5Xn9I1FdYBXDoT+P1iayiqFJ7mEllFgaxpH5zlzWODZT KImo0lDRly2DcGcgyWDsFxYjSvPtDnbTdc0zntMCHXblH2ZoAdutil00mD/SJGya TssJryhudabz40FIFTXR =3kd0 -----END PGP SIGNATURE----- --HBoKUtE0wg8OgvF8HaIeneDahTDhXpNSt--
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