Adamnp

SCSI vs SATA, Which is Faster?

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If Sata is so great then why is it that SCSI rules in every server?

Liam, i follow you except here:

4x7200 drives in a raid (i presume you mean raid0) do not perform that great.

Benchmarks are not absolute either.

Me, i have and probably always will have SCSI's in my computers.

Bottom line is : if you need heavy duty drives, SCSI is the way to go. I cannot imagine some AS400 loaded with Sata drives when a few hundred (thousand) people are hitting enter on their keyboard....

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If Sata is so great then why is it that SCSI rules in every server?

Because it usually makes more sense to use SCSI in servers than IDE or SATA. It doesn't mean SCSI is any better for a desktop PC than IDE/SATA. You cannot compare a desktop PC with an AS/400 or even a small file server for 20 users. SCSI controllers are often also better supported on various OS'es than IDE/SATA but for entry-level servers SATA will replace SCSI in many cases.

A few years ago I threw out my Cheetah 36ES (18 GB) for my Deskstar 75 GXP (15 GB) and there were only 2 things different. Less noise and admittedly a dead Deskstar after a few months. Couple of months ago though I cloned my XP installation onto a current 10k SCSI drive I borrowed from work (a 36 GB Fujitsu it was I think) and besides the noise I noticed little difference between the SCSI drive and my 40 GB 7200.7 with a mere 2 MB cache.

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OTOH I have a server running at my girlfriend's work with a couple of 9 GB SCSI drives on a ServeRAID controller. Without a doubt a mirror or current IDE drives would have been faster but:

-they don't need all that much speed

-the RAID controller is very well supported (and cost me only €18)

-I can add as much drives as I have cable positions

-if the mainboard of the server crashes I can yank out the RAID controller and drives and install it in any other PC and it will work

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Simple answer: SCSI.

The interface is faster and the 15k SCSI drives rule the raw performance charts.

Now.....

Which is faster?

A 2005 Dodge Viper or my 2001 F-150?

Well that's easy... my F-150.

Sounds insane. What?! The F-150!?!!11111

Since I am usually limited to 80 mph on the interstate highway, I can go over 600 miles in my truck (and have done so) without refueling. I can only go about 350 miles in that Viper, before I need to stop for fuel.

If you drive near the speed limit, the Viper is a poor decision.

What if I want 5 people to go with me on my trip? Viper or F-150?

Well, you would need to travel 9 times the distance in the Viper (4.5 round trips)

The F-150 is still faster.

If you live in a congested city, which is more important? 0-60mph time or idle time?

5 seconds to 60 mph? Or the engine needs to run for 5 hours?

So... faster how? ;)

Gaming? Office use? Video Editing (Uncompressed real-time)?

By the raw numbers (e.g. 'torque', 'horsepower', etc.) the winner is SCSI.

But why waste money on a Viper, when a Prius works better for *you*?

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I've been watching this thread for a while now. Time for me to chime in...

The question cannot be answered. "Performance" is a function of many different parameters including the interface, the drive type, the drive price, and the application/workload.

If you don't specify the requirements, you can't answer the question.

The problem is complicated by the fact that the two interface types serve very different market segments. ATA is intended for the low cost segment, and so it's pretty much universally associated with lower-performance mechanics. This handicaps ATA drives in a way that is hard to factor out when making comparisons of the interface, since the drive mechanics dictate so much of the performance equation.

ATA is without a doubt a more "efficient" protocol. SCSI operates on a shared resource, and this demands overhead that is not a requirement on a SATA point-to-point connection. But SCSI scales and ATA does not (you need additional ATA controllers). SCSI is faster (Ultra320) than 1.5gb SATA, but it isn't faster than 3gb SATA (or SAS, or 4gb Fibre). ATA allows operations on Cache (like dirty reads) that SCSI prohibits, so ATA can be faster on some Cache oriented workloads. The lower overhead of ATA improves bus utilization on short-transfer workloads, so ATA can be faster on 100% cache hit reads and bursty writes. SCSI goes to deeper queue depth, and can deliver substantially higher sustained random IOPS because of this (and the fact that SCSI mechanics are much faster than ATA).

The only thing you can say that's even slightly definitive is, for most desktop users the advantages of SCSI don't matter to their workloads, and they can even be a hinderance. If you don't need SCSI's features, ATA will be as good, possibly better, for much less money.

So which performs better? It depends on what you want to do with it, and how much you want to spend.

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The question cannot be answered.  "Performance" is a function of many different parameters including the interface, the drive type, the drive price, and the application/workload. 

I believe that I said something to that effect way back on page one....

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