Date: Wed, 19 Nov 2014 12:44:22 -0600 From: Aidan Scheller <aidan@aodhandigital.com> To: Mark Martinec <Mark.Martinec+freebsd@ijs.si> Cc: freebsd-stable@freebsd.org Subject: Re: 10.1 fresh install and 4k alignment Message-ID: <CADNPKbPC7h7Q0WRQM7sFSPUPMNjAJ7ERkzUS7zkxNJJBPa-wjg@mail.gmail.com> In-Reply-To: <ead753e90b2b74b169af2fb04c525c9e@mailbox.ijs.si> References: <A2328132-EC43-4E27-8D01-A4D774634598@punkt.de> <ead753e90b2b74b169af2fb04c525c9e@mailbox.ijs.si>
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Hi Mark, Did you submit a PR for this? I'm not able to find anything related in Bugzilla and am wondering we should do so. Thanks, Aidan On Wed, Nov 19, 2014 at 8:32 AM, Mark Martinec <Mark.Martinec+freebsd@ijs.si > wrote: > Patrick M. Hausen wrote: > >> Hi, all, >> >> I just installed a new machine with 10.1-RELEASE using the memstick >> installer >> and chosing ZFS mirror root as the disk layout. >> >> I did check the "4k" option, watched the installer do the necessary gnop >> dance >> and the pool seems to be OK: >> >> root@seleniumhub:~ # zdb | grep ashift >> ashift: 12 >> >> But this puzzles me a bit: >> >> root@seleniumhub:~ # gpart list ada0 >> Mediasize: 524288 (512K) >> Sectorsize: 512 >> ... >> Providers: >> 1. Name: ada0p1 >> Mediasize: 524288 (512K) >> Sectorsize: 512 >> ... >> end: 1057 >> start: 34 >> ... >> 3. Name: ada0p3 >> Mediasize: 465747565056 (434G) >> Sectorsize: 512 >> ... >> type: freebsd-zfs >> ... >> end: 976773134 >> start: 67109922 >> >> None of the start sector numbers is a multiple of 8, neither are the end >> sectors >> a multiple of 8 minus 1. >> >> So the pool uses a 4k block size but it starts on an odd multiple of >> 2k on the platter >> - do I see this correctly? >> >> Isn't it absolutely necessary that the simulated 4k blocks are laid >> out so that the first >> is made from 512 byte sectors 0-7, the second from 8-15 and so on? >> >> Then why does the installer start the first partition at 512 byte >> sector 34? While I'm at >> it, this magic number is everywhere in the older documentation, e.g. >> for manually >> installing FreeBSD 8 with gptzfsboot - where does that 34 come from? It's >> not >> a power of 2 nor is it one of the historical CHS magic numbers that would >> mean >> a cylinder boundary or similar. Size of the GPT partition table itself? >> >> Is this a bug in the installer? Will I still have to layout the disks >> manually if I want 4k >> alignment? What's a good offset for the first partition in this case? >> Anything bigger >> than 34 that's a multiple of 8 - 40 or 64? >> >> Thanks in advance >> Patrick >> > > > Reported on 2014-10-10, but was apparently forgotten/ignored: > > "GPT partitions not 4k aligned by 10.1-RC1 installer" > https://lists.freebsd.org/pipermail/freebsd-stable/2014- > October/080509.html > > > Mark > > > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" >
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