Date: Mon, 27 Jun 2005 21:19:04 -0400 From: Jarrod Martin <jmartin37@speakeasy.net> To: Martin Nilsson <martin@gneto.com> Cc: Artem Kuchin <matrix@itlegion.ru>, freebsd-stable@freebsd.org Subject: Re: SATA vs SCSI ... Message-ID: <42C0A588.3060407@speakeasy.net> In-Reply-To: <42BF9EC2.1060203@gneto.com> References: <20050626233114.G57847@ganymede.hub.org> <004201c57adf$49367ad0$0c00a8c0@artem> <42BF9EC2.1060203@gneto.com>
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Martin Nilsson wrote: > Artem Kuchin wrote: > >> Marc G. Fournier <scrappy@hub.org> wrote: >> >> For the last 6 month i really think that if you don't need something >> high-end scsi then you should go for SATA. > > > Fair enough if you don't need high-end yoy shuld go lowend. But read on.. > >> 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. > > > That is a well known fact. It is also a totally useless parameter for > server use. > > >> Acatuallty, modern hdds use the same mechanics for sata and scsi > > > versions of them. The brains > > This is simply not true. There were a couple of drives about 10yrs ago > where this was true eg. Quantum Lightning which were available in both > IDE and SCSI > > Todays SCSI drives have _nothing_ in common with SATA/ATA drives. > >> However, when it comes to random read/writesscsi wins because of > > > command queueing. > > And faster accesstime and higher rotational speed (lower latency) you > simply can't compare a 7200rpm drive to a 15000rpm drive no matter > what interface it has. > >> Recently SATA with NCQ became widly available. Test show that some of >> those >> SATA disks with NCW ***WIN*** over scsi 320. > > > To use NCQ drive, controller and OS needs to support it, only a few > controllers supports NCQ and FreeBSD have no support at all! this brings up a very interesting question. for anyone who has read up on the SATA-II (or SATA-IO, as it has been renamed...) standard... not all SATA-II harddrives have to support NCQ, nor do they have to have the 3Gb/s transfer rate. now does this also mean that motherboards which have SATA-II compliant chips don't have to support those features either? how do you know you're actually getting these features? i think perhaps the standard has been a little messed up since they didn't force a set of standards to be included in a "SATA-II" drive... > >> The test envolve artificialy randomread/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. > > > The tests on tomshardware are windows single user centric, they never > test server workloads, their audience are kids who plays games... > >> 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. > > > Want something cheap with lots of space? SATA > Want something that works and is fast? SCSI > > Using SATA for databases and mailservers is going to give you bad > performance. > > Regards, > Martin > also, if anyone has read the reviews at anandtech.com there has been lots of evidence that shows that, on certain operations, NCQ actually performs worse in real world tests. with the Maxtor DiamondMax 10, Seagate 7200.8 and several other NCQ drives, the NCQ caused lag in certain disk operations. NCQ, at least for now, is highly over-rated.
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