Date: Wed, 25 Oct 2006 15:24:55 +0200 From: Guido van Rooij <guido@gvr.org> To: "Patrick M. Hausen" <hausen@punkt.de> Cc: Rink Springer <rink@freebsd.org>, freebsd-stable@freebsd.org Subject: Gmirror performanc (was Re: Gmirror question) Message-ID: <20061025132455.GA52157@gvr.gvr.org> In-Reply-To: <20061025104829.GA41873@hugo10.ka.punkt.de> References: <20061025100759.GA50625@gvr.gvr.org> <20061025101801.GE23885@rink.nu> <20061025103905.GB50937@gvr.gvr.org> <20061025104829.GA41873@hugo10.ka.punkt.de>
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On Wed, Oct 25, 2006 at 12:48:29PM +0200, Patrick M. Hausen wrote: > You don't need to. > > If your bsdlabel partition is N sectors in size, the gmirror > object will have size N - 1. Newfs will not be able to write > to that last sector. You newfs the finished mirror device, > not the individual partitions. Indeed. How stupid from me. Anyway, I created a gm device and a partition. Now the read performance is not what I'd expect. I have the partition on two SATA devices on different controlers. I get around 60MB/s for each disk. I can get that speed from both disks simultaneously. Now when I dd from the gm device, I don't get any speed higher than that. I tried with -b split -s <various sizes>, -b round-robin, -b load. (dd-ing as done with a bs of 1m; I see the transaction size is 128Kb, unless the split method is used, in which case the transaction size gies down. When round-robin is used, the transaction size is 128Kb/s, but the number of transaction per second goes down.). I cannot explain why I should not get a higher read speed. Anyone? -Guido
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