Date: Mon, 27 Jun 2005 10:13:04 +0400 From: "Artem Kuchin" <matrix@itlegion.ru> To: "Marc G. Fournier" <scrappy@hub.org>, <freebsd-stable@freebsd.org> Subject: Re: SATA vs SCSI ... Message-ID: <004201c57adf$49367ad0$0c00a8c0@artem> References: <20050626233114.G57847@ganymede.hub.org>
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Marc G. Fournier <scrappy@hub.org> wrote: > looking at the specs between two cards, the SATA card(s) seem to rate > ~100-150MB/s on each channel (if I'm reading right), with both the > 3Ware and ICP cards having 4 individual channels ... looking at the > SCSI cards, they are rated at 320MB/s, but that is total for the SCSI > bus itself, right? > > So, if I have three drives on a SCSI bus, each 'maxing out evenly', > I'd be cap'd at about the same 100MB/s per drive, no? > > In fact, looking at the SATA 2.x specs, each chanell there is rated at > 300MB/s, which, again, if I could 'max out evenly', could seriously > blow away the SCSI bus itself ... > > *If* I'm reading this right ... ? For the last 6 month i really think that if you don't need something high-end scsi then you should go for SATA. There are test on sites such as Tom's hardware guide and ixbt.com. They show then on sequrncial read there is no difference between scsi and sata. Acatuallty, modern hdds use the same mechanics for sata and scsi versions of them. The brains (electronics) on the hdds are different of course. However, when it comes to random read/writes scsi wins because of command queueing. This was an issue until recently, Recently SATA with NCQ became widly available. Test show that some of those SATA disks with NCW ***WIN*** over scsi 320. The test envolve artificialy random read/write tests as well as real application benchmarking. I din't rememeber where excatly i saw the tests on those site, but you could search. So, my opinion, workstation never needs SCSI and every server MUST be on mirror or RAID5 and there you should use SATA with NCQ drivers unless, your applicaton is really weird and needs something extremely speedy. Then, however, you could go for RAID 0+1 and get perfomance that SCSI will never get you. -- Regards, Artem Kuchin IT Legion Ltd. Moscow, Russia www.itlegion.ru matrix@itlegion.ru +7 095 232-0338
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