Date: Wed, 20 Jun 2018 19:37:20 +0200 From: Miroslav Lachman <000.fbsd@quip.cz> To: Warner Losh <imp@bsdimp.com> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: iostat busy value calculation Message-ID: <55731ed7-c9f5-1e39-9c09-b522e58b97a1@quip.cz> In-Reply-To: <CANCZdfqs%2BkJh5MsiGnXUh=9VVNy9qqc3eGCPYftS5gp5nay%2Bxg@mail.gmail.com> References: <98c4156c-d2f0-f0c6-b859-9cea8ec29a42@quip.cz> <CANCZdfqs%2BkJh5MsiGnXUh=9VVNy9qqc3eGCPYftS5gp5nay%2Bxg@mail.gmail.com>
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Warner Losh wrote on 2018/06/20 18:13: > > > On Wed, Jun 20, 2018 at 8:55 AM, Miroslav Lachman <000.fbsd@quip.cz > <mailto: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). Yes, I am aware of this issue. This percentage is just "is it slightly loaded or heavily loaded" indicator. Miroslav Lachman
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