Re: SATA vs SCSI



Folkert Rienstra wrote:
<tm4525@xxxxxxx> wrote in message news:1138381534.917697.32970@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
Arno Wagner wrote:
Previously Rob Nicholson <rob.nicholson@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I know, that old chestnut :-) We're currently running a five year old Dell
PowerEdge 4400 server with 5 x 70GB Hitachi Ultra 160 SCSI drives in RAID-5
giving us ~280GB disk space. This server hosts our file share, SQL 7 and
Exchange 5.5 services.

But the time has come to plan for the future and upgrade where appropriate.
We're looking at switching to Windows 2003 and buying another server to host
SQL Server and Exchange. We're at about 40 users at the moment but have
plans to grow to 100+

Simple question, complex answer I guess: is it still best to stick with SCSI
or consider SATA?

Stay SCSI. SATA may look the same in some benchmarks, but the
fact of it is that SATA is a cheap, mass-market product, while
SCSI is a professional product. It is designed with a different
mind-set. True, SCSI also fails sometimes. Also true SCSI may
not be that much faster today. But overall you get something
different when profit margins per unit are significanrt and
manufacturer care to have their products viewed as reliable
by people that are willing to pay a lot.


Thats just about the dumbest thing I've ever heard.

And another one that will be banned from playing in Arnie's sandbox.


The reason SCSI is not as "mass marketed" is because for single drive
systems; by far the most prevalent, SCSI is more expensive and offers
no advantages. The reality is that SCSI is less stable, not because of
the technology, but because far fewer people use it so the drivers and
subsystems are not as well supported in any of the major OS.

Uhuh.
You think that 20+ years of existence is not enough to learn how SCSI works.

I wonder what happens if you apply this chain of thought to RAID.

My personal experience is that SCSI drives seem to fail at a much higher
rate than IDEs, but thats likely due to higher RPMs. In fact you can
make a strong business case for using slower drives in many cases as
the failure rate of slower drives is must less than "high speed" drives.

I don't know the specific performance advantages for SCSI vs SATA on
multi disk systems (I'm sure it varies from setup to setup, OS to OS

and MB to MB) but to reject SATA because you think SCSI is more
professional or more technically sound is simply ridiculous.

Actually, applying your chain of thought it should be tremendously more sound
than SATA just because it has been around for so much longer than SATA.

No, thats not the case, because people aren't running with equipment
and operating systems that are 20 years old. New SCSI MBs and
controllers require new and ongoing support as do other hardware
choices. The more samples you have the more likely that you will have
found all of the problems. There are far more samples for any given
SATA subsystem than there is for any given SCSI subsystem. People have
been using RS-232 serial communications for much longer than USB, so
does that mean that RS-232 devices are more reliable than USB devices?
Of course not; that's just plain stupid.

The most "reliable" system is one with a large single disk, and SCSI is
not a higher performance solution on a single disk system. A multiple
disk system has more parts to fail, has more layers of software to have
bugs, draws more power and generates more heat. SCSIs performance
advantages are only with multiple-disk systems. We use large Sata disks
and mirror them with rsync. Inexpensive, reliable and fast (enough).

Most people who've never done any actual testing have wrong ideas about
just about everything. Your logic is the same logic that says that a
system with 2 cpus must be faster than a system with 1 cpu. It seems
logical, but its simply not necessarily the case, and often isn't the
case at all.

I also find it comical that the same clan of folks who whine about the
power consumption advantages of AMD processors have no like opinions
when it comes to other equipment. Its a lot like politics; the case
that fits whatever it is you're doing is the one that suits you for the
present conversation.

TM

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