Date: Tue, 15 Jan 2013 16:05:18 -0600 From: "Matthew D. Fuller" <fullermd@over-yonder.net> To: Dieter BSD <dieterbsd@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: IBM blade server abysmal disk write performances Message-ID: <20130115220518.GF3400@over-yonder.net> In-Reply-To: <CAA3ZYrACHLU-4OyhLdD%2BmfCDR_kubBg-AiVcopL-skqDurE7YA@mail.gmail.com> References: <CAA3ZYrACHLU-4OyhLdD%2BmfCDR_kubBg-AiVcopL-skqDurE7YA@mail.gmail.com>
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On Tue, Jan 15, 2013 at 12:03:33PM -0800 I heard the voice of Dieter BSD, and lo! it spake thus: > > But dmesg claims "Command Queueing enabled", so you should be > getting more than one op per rev, and writes should be fast. Queueing would only help if your load threw multiple ops at the drive before waiting for any of them to complete. I'd expect a dd to a raw device to throw a single, wait for it to return complete, then throw the next, leading to no more than 1 op per rev. (possibly less, with sufficiently fast revs and a sufficiently slow system, but that's a pretty unlikely combo with platter drives and remotely modern hardware unless it's under serious load otherwise) -- Matthew Fuller (MF4839) | fullermd@over-yonder.net Systems/Network Administrator | http://www.over-yonder.net/~fullermd/ On the Internet, nobody can hear you scream.
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