Date: Mon, 03 Oct 2005 11:57:14 -0300 From: =?ISO-8859-1?Q?Tulio_Guimar=E3es_da_Silva?= <tuliogs@pgt.mpt.gov.br> To: freebsd-performance@freebsd.org Subject: Re: dd(1) performance when copiing a disk to another Message-ID: <434146CA.8010803@pgt.mpt.gov.br> In-Reply-To: <004701c5c77e$a8ab4310$b3db87d4@multiplay.co.uk> References: <20051002170446.78674.qmail@web30303.mail.mud.yahoo.com> <004701c5c77e$a8ab4310$b3db87d4@multiplay.co.uk>
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This is a multi-part message in MIME format. --------------030603030606000800030004 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Steven Hartland wrote: > ----- Original Message ----- From: "Arne Wörner" <arne_woerner@yahoo.com> > >> That seems to be 2 or about 2 times faster than disc->disc >> transfer... But still slower, than I would have expected... >> SATA150 sounds like the drive can do 150MB/sec... > > > LOL, you might want to read up on what SATA150 means. > In short it the max throughput the interface can sustain. It is NOT > what you can get of a single disk which is still fare from that, > SATA disk transfer rates typically 30 -> 50MB/s sustained. > > Steve Indeed. In other words, that represents the max transfer rates between the SATA controller and the disk´s controller (at best, you´ll get close to it when reading from the disk´s onboard cache), but the media will always be much slower. But just to clear out some questions... 1) Maxtor´s full specifications for Diamond Max+ 9 Series refers to maximum *sustained* transfer rates of 37MB/s and 67MB/s for "ID" and "OD", respectively (though I couldn´d find exactly what it means, I deduced that represents the rates for center- and border-parts of the disk - please correct me if I´m wrong), then your tests show you´re getting the best out of it ;) ; 2) Mr. Hartland mentioned the numbers to be good for a single drive, therefore it´s a bit better for a disk-to-disk, where the limit should be the slower disk´s performance. I couldn´t look for the specs of the Toshiba since I didn´t have the exact model, but I would expect it to be equal or faster than the Maxtor, since it does not appear to be a bottleneck. One last thought, though, for the specialists: iostat showed maximum of 128KB/transfer, even though dd should be using 1MB blocks... is that an expected behaviour? Shouldn´t iostat show 1024Kb/t, then? Thanks for your attention, Tulio G. da Silva --------------030603030606000800030004--
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