SATA vs SCSI ...

[Brett Wildermoth]

One other point worth mentioning is that on SATA all transactions are host 
generated, while with SCSI devices any device can start a transaction. 
Transactions can be interleaved better resulting in a higher average 
throughput.

On Mon, 27 Jun 2005 01:19 pm, owner-freebsd-stable at freebsd.org wrote:
> On Sun, Jun 26, 2005 at 11:34:22PM -0300, Marc G. Fournier 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?
>
> It is dependant of the card too. You can get a 3 channel Ultra320 card for
> 3 drive RAID 5...
>
> > 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 ...
>
> That is a theory...
>
> > *If* I'm reading this right ... ?
>
> And now from my practice:
>
> 1) You CAN'T get maximal throuput from 150/160 MB/s bus - the is no such
> drives today at the market.
>
> 2) Avg. seek and access time of 7200 SATA drives are FAR BELOW such of old
> Seagate Cheetah/Maxtor Athlas 10K. So is a situation with a WD Raptor 10K
> SATA too - they are SLOWER! (I'm not shure why, but from my test:
>
> 2xPIII-1.4/1G RAM/2x36G Cheeta 10K in RAID 1 (AMR Express; One U160
> channel) ws.
> 2xXeon 3.0/2G RAM/2x72G Raptor in RAID 1 (Intel SRCS16; Separate SATA-150
> channel for each drive)
>
> Ports three checkout is about 20% faster on the first comp.
>
> As an result: If you need to have FAST disk subsystem - buy SCSI. If you
> need large storage or you don't want to pay to much money - buy SATA.
>
> Best Ragards,
>
> Serg N. Voronkov,
> Sibitex JSC.
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-- 
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 Brett Wildermoth BEng(ME) MPhil
 Lecturer / PhD Student
 School of Microelectronic Engineering
 Faculty of Engineering and Info. Tech.
 Ph. +61 7 3875 5063, Fax. +61 7 3875 5384
 Email. B.Wildermoth at grifith.edu.au
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