Date: Wed, 17 Jul 2013 10:00:49 -0700 From: =?ISO-8859-1?Q?Gezeala_M=2E_Bacu=F1o_II?= <gezeala@gmail.com> To: Warren Block <wblock@wonkity.com> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org> Subject: Re: Slow resilvering with mirrored ZIL Message-ID: <CAJKO3mWqUTB22Hu=Ce%2By_0Om96Ai1ZgLL_3dEcC4p6DXoy3YLQ@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1307161935020.84500@wonkity.com> References: <CABBFC07-68C2-4F43-9AFC-920D8C34282E@unixconn.com> <51D42107.1050107@digsys.bg> <2EF46A8C-6908-4160-BF99-EC610B3EA771@alumni.chalmers.se> <51D437E2.4060101@digsys.bg> <E5CCC8F551CA4627A3C7376AD63A83CC@multiplay.co.uk> <CBCA1716-A3EC-4E3B-AE0A-3C8028F6AACF@alumni.chalmers.se> <20130704000405.GA75529@icarus.home.lan> <C8C696C0-2963-4868-8BB8-6987B47C3460@alumni.chalmers.se> <20130704171637.GA94539@icarus.home.lan> <2A261BEA-4452-4F6A-8EFB-90A54D79CBB9@alumni.chalmers.se> <20130704191203.GA95642@icarus.home.lan> <43015E9015084CA6BAC6978F39D22E8B@multiplay.co.uk> <CAOjFWZ4obK1cSmvTpW%2Bt4xKdMf%2BkJV5w-sujDT1AZoepj%2B5YrA@mail.gmail.com> <3CFB4564D8EB4A6A9BCE2AFCC5B6E400@multiplay.co.uk> <51D6A206.2020303@digsys.bg> <CAOjFWZ5CWV3UZRppM3nTehfTPaw1N%2Bw6LjsEZZGxE16DOkS%2BGA@mail.gmail.com> <CAJKO3mW=ahm7sBdjGc-b2tN3D7%2BQH7gR7UPt24RsqUdZf=%2BjvA@mail.gmail.com> <alpine.BSF.2.00.1307161935020.84500@wonkity.com>
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On Tue, Jul 16, 2013 at 6:47 PM, Warren Block <wblock@wonkity.com> wrote: > On Tue, 16 Jul 2013, Gezeala M. Bacu=F1o II wrote: > > On Fri, Jul 5, 2013 at 6:08 PM, Freddie Cash <fjwcash@gmail.com> wrote: >> >> >>> ZFS- on-Linux has added this as "-o ashift=3D" property for zpool creat= e. >>> >>> There's a threat on the illumos list about standardising this s across >>> all >>> ZFS- using OSes. >>> >>> >>> >>> +1 on this. We tested zfs-on-linux last year and it does automatically >> handle disk partitioning for correct alignment. What we do is just add >> ashift=3D12 option during zpool create. No more gpart/gnop/ashift/import >> steps. >> >> http://zfsonlinux.org/faq.**html#**HowDoesZFSonLinuxHandlesAdvace** >> dFormatDrives<http://zfsonlinux.org/faq.html#HowDoesZFSonLinuxHandlesAdv= acedFormatDrives> >> >> >> Back to FreeBSD ZFS, >> >> After reading the thread, I'm still at a loss on this (too much info I >> guess).. regarding gpart/gnop/ashift tweaks for alignment, do we still >> need >> to perform gpart on newly purchased (SSD/SATA/SAS) Advanced Format drive= s? >> Or, skip gpart and proceed with gnop/ashift only? >> > > If ZFS goes on a bare drive, it will be aligned by default. If ZFS is > going in a partition, yes, align that partition to 4K boundaries or large= r > multiples of 4K, like 1M. > > Your statement is enlightening and concise, exactly what I need. Thanks. > The gnop/ashift workaround is just to get ZFS to use the right block size= . > So if you don't take care to get partition alignment right, you might en= d > up using the right block size but misaligned. > > And yes, it will be nice to be able to just explicitly tell ZFS the block > size to use. We do add the entire drive (no partitions) to ZFS, perform gnop/ashift and other necessary steps and then verify ashift=3D12 through zdb. The gpart/gnop/ashift steps, if I understand correctly (do correct me if I'm stating this incorrectly), is needed for further SSD performance tuning. Taking into consideration leaving a certain chunk for wear leveling and also if the SSD has a size that may be too big for L2ARC.
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