Date: Wed, 20 Jun 2018 10:13:40 -0600 From: Warner Losh <imp@bsdimp.com> To: Miroslav Lachman <000.fbsd@quip.cz> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: iostat busy value calculation Message-ID: <CANCZdfqs%2BkJh5MsiGnXUh=9VVNy9qqc3eGCPYftS5gp5nay%2Bxg@mail.gmail.com> In-Reply-To: <98c4156c-d2f0-f0c6-b859-9cea8ec29a42@quip.cz> References: <98c4156c-d2f0-f0c6-b859-9cea8ec29a42@quip.cz>
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On Wed, Jun 20, 2018 at 8:55 AM, Miroslav Lachman <000.fbsd@quip.cz> wrote: > I would like to know how the value of disk "busy" is calculated? > > I want to use values from iostat in the monitoring (zabbix). > iostat shows averages by default and the last column is "busy %", but the > first output contains averages from the system boot til now. > %busy comes from the devstat layer. It's defined as the percent of the time over the polling interval in which at least one transaction was awaiting completion by the lower layers. It's an imperfect measure of how busy the drives are (in ye-olden days, before tagged queuing and NCQ, it was OK because you had THE transaction pending and it was a good measure of how utilized things were. Now with concurrent I/O in flash devices, it's only an imperfect approximation). Warner
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