Date: Fri, 19 Feb 2016 14:50:21 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: n.corvini@gmail.com Cc: freebsd-fs@freebsd.org Subject: Re: Zfs heavy io writing | zfskern txg_thread_enter Message-ID: <201602192250.u1JMoLjQ079393@gw.catspoiler.org> In-Reply-To: <CAM1TVW-yOvU6VM19PadD5ygsv2-Vb-_8T7SKjcsP7Ov0Q5A5SQ@mail.gmail.com>
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On 19 Feb, Niccolò Corvini wrote: > Hi, first time here! > We are having a problem with a server running FreeBsd 9.1 with ZFS on a > single sata drive. Since a few days ago, in the morning the system becomes > really slow due of a really heavy io writing. We investigated and we think > it might start at night, maybe correlated to to crondaily (standard) but we > are not sure. After a few hours the situation returns to normal. > Any help is much appreciated > The machine is a Intel Xeon E5-2620 with 36GB of RAM, the HDD is a 2TB an > is half full. The only way that you should get a lot of write traffic during the daily periodic runs is if atime updates are enabled. I don't know what the default was for FreeBSD 9.1, but recent versions of FreeBSD disable atime updates on ZFS everywhere except /var/mail. What does zfs get -o all atime say? The other thing I was going to ask is how full the disk is. ZFS performance degrades quite a bit when the disk gets close to full. At 50% of capacity, you shouldn't be running into that problem.
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