Date: Fri, 10 May 2019 12:01:22 +0200 From: Miroslav Lachman <000.fbsd@quip.cz> To: Alan Somers <asomers@freebsd.org> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>, Dimitry Andric <dim@freebsd.org> Subject: Re: ZFS... Message-ID: <8e443083-1254-520b-014d-2f9a94008533@quip.cz> In-Reply-To: <CAOtMX2ip_G0afh_4AaYcQt4=zX4qkCTfs0qb66DpCgcALZXS5g@mail.gmail.com> References: <30506b3d-64fb-b327-94ae-d9da522f3a48@sorbs.net> <d0118f7e-7cfc-8bf1-308c-823bce088039@denninger.net> <2e4941bf-999a-7f16-f4fe-1a520f2187c0@sorbs.net> <20190430102024.E84286@mulder.mintsol.com> <41FA461B-40AE-4D34-B280-214B5C5868B5@punkt.de> <20190506080804.Y87441@mulder.mintsol.com> <08E46EBF-154F-4670-B411-482DCE6F395D@sorbs.net> <33D7EFC4-5C15-4FE0-970B-E6034EF80BEF@gromit.dlib.vt.edu> <A535026E-F9F6-4BBA-8287-87EFD02CF207@sorbs.net> <a82bfabe-a8c3-fd9a-55ec-52530d4eafff@denninger.net> <a1b78a63-0ef1-af51-4e33-a9a97a257c8b@sorbs.net> <CAMPTd_A7RYJ12pFyY4TzbXct82kWfr1hcEkSpDg7bjP25xjJGA@mail.gmail.com> <d91cf5@sorbs.net> <7D18A234-E7BF-4855-BD51-4AE2253DB1E4@sorbs.net> <E68600B3-F856-4909-AB6E-BDFCD8AAAB43@punkt.de> <805ee7f1-83f6-c59e-8107-4851ca9fce6e@quip.cz> <E980141F-48D9-4870-8FE1-9A5610F12826@FreeBSD.org> <5de7f3d3-b34c-0382-b7d4-b7e38339649b@quip.cz> <CAOtMX2ip_G0afh_4AaYcQt4=zX4qkCTfs0qb66DpCgcALZXS5g@mail.gmail.com>
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Alan Somers wrote on 2019/05/09 14:50: [...] > On 11.3 and even much older releases, you can greatly speed up scrub > and resilver by tweaking some sysctls. If you have spinning rust, > raise vfs.zfs.top_maxinflight so they'll do fewer seeks. I used to > set it to 8192 on machines with 32GB of RAM. Raising > vfs.zfs.resilver_min_time_ms to 5000 helps a little, too. I have this in sysctl.conf vfs.zfs.scrub_delay=0 vfs.zfs.top_maxinflight=128 vfs.zfs.resilver_min_time_ms=5000 vfs.zfs.resilver_delay=0 I found it somewhere in the mailinglist discussing this issue in the past. Isn't yours 8192 too much? The machine in question has 4x SATA drives on very dump and slow controller and only 5GB of RAM. Even if I read this vfs.zfs.top_maxinflight: Maximum I/Os per top-level vdev I am still not sure what it really means and how I can "calculate" optimal value. As Michelle pointed there is drawback when sysctls are optimized for quick scrub, but this machines is only running nightly backup script fetching data from other 20 machines so this scrip sets sysctl back to sane defaults during backup sysctl vfs.zfs.scrub_delay=4 > /dev/null sysctl vfs.zfs.top_maxinflight=32 > /dev/null sysctl vfs.zfs.resilver_min_time_ms=3000 > /dev/null sysctl vfs.zfs.resilver_delay=2 > /dev/null At the and it reloads back optimized settings from sysctel.conf Miroslav Lachman
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