SATA vs SCSI ...

[Artem Kuchin]

Marc G. Fournier <scrappy at 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 at itlegion.ru
+7 095 232-0338