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5400rpm Hard Drive with 3GB SATA ... what is the point?

Posted on 2012-03-11
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Last Modified: 2012-04-10
Ok, I was just puttering around with some hardware today... and noticed that one of my  old 160GB hard drives was 5400RPM (so SLOW), but that it was also SATA 3GB/s...

OK, so what is the point of having insane throughput on a HD with  the second slowest RPM speed now available (I think that there used to be 4200RPM drives, or something like that).

Ok, so why do manufacturers do that? is there any benefit or is it just that the hardware standard these days is just becoming 3GB/s, so the manufacturers buy them for the same price as 1.5 GB/s hardware, for example, and gain a "misleading" selling point because they get to put 3GB/s on the HD box?

For my sanity, and instruction, can an expert please clarify this?

Thanks!
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Question by:vanauden
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by:lojk
ID: 37706664
the maintenance cost of keeping 2 kinds of controllers in stock for their hardrives and making sure the correct one is used for each model is probably higher than the cost difference between 1.5 and 3.0 controller.

Also a lot depends on what the manafacturer is expecting you to connect it too - he wont support old standards if he knows you wont (need to) use them as this backwards compataiblity comes with complexity and cost issues too. That is why serial ports are disappearing from PCs, (nearly) everyone uses USB these days.

And yes, the cynical bit of me agrees people always go (pay) for a bigger number if there is a choice, even if there isnt a reason (that they understand).
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by:davorin
davorin earned 100 total points
ID: 37706686
It is all about production price. There is not so big difference in price between different SATA versions of controllers, they are backward compatible, so it is cheaper to have one production and distribution line for SATA2 disks than two lines - SATA1 and SATA2.

This days is SATA3 geting more and more standard with 6Gb/s (not GB/s).
The speed of disk depends of the speed of transferring data from platters to buffer, which does not depends only on rotation speed but also on data density on disk platters.
So you can expect that your 160GB disk can be around 10 times slower than 1.5TB disk even if they both rotate at 5400 rpm.
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by:IanTh
ID: 37706705
what kind of drive was it I have seen some really bad drives in the past so these days I tend to stick to samsung hdd's as even when I did have a problem their customer support was spot on and swapped the drive whithout a question when they found the serial number inside the warranty term

The controllers hdd makers use also vary in quality so find a brand lear to trust it and stick with that until you find a real problem and see if that problem gets sorted if it does its a good brand. Also there are real differences in some cheap motherboards to mid level boards again its down to cost

A few years ago I did a hdd swap out project for failing drives it was a test for the hdd manufacturer if they should continue making drives and their failure wait was way over 50% which meant they got out of hdd production as it was costing too much I later that the had a microcode fix so it was a very political issue I felt
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by:Callandor
Callandor earned 100 total points
ID: 37706726
The interface speed (3Gbit/sec) has nothing to do with how fast the drive can transfer data in a sustained manner - that depends a lot on drive rotation speed and data density, as others have noted.  Even 7200 rpm drives max out around 90 MBytes/sec, or 720 Mbits/sec, and that's under ideal conditions.  The interface does help IF there are a lot of small files which happen to be in the cache, or if the drive is an SSD.  Otherwise, it's just a matter of maintaining a compatible interface which is cheap to manufacture.
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garycase earned 300 total points
ID: 37707271
Your question is equally valid for 7200rpm drives -- since even SATA-1's transfer speed is far faster than the sustained transfer speed of any drive.

But that's not the point.    As Callandor outlined above, the sustained transfer speed of a drive depends on the rotational rate, and the areal density of the data (how tightly "packed" the bits are on the platter).       The interface speed (IDE, SATA, SATA-2, SATA-3, etc.) makes NO apprecial difference, as long as it's above the sustained data rate.    The only time data is actually transferred at the interface rate is when transfers are between the PC and the disk's buffer => a VERY small percentage of disk I/O.

If your 160GB drive is slow, it's likely due more to low areal density and/or badly fragmented files more than that fact it's a 5400rpm drive.    A 7200rpm drive is only 1/3rd faster than a 5400 rpm drive with the same areal density.

The big difference between interface speeds and sustained data rates for modern interfaces (SATA-2, SATA-3, SAS) is why port multipliers are becoming more common ... there's no performance impact of allowing 2, 3, or 4 drives to share a single SATA port when the port is fast enough to let all of the drives run at their full sustained rate.

By the way, the comment above that  "... you can expect that your 160GB disk can be around 10 times slower than 1.5TB disk "  is VERY wrong.     That would be true if both were single-platter drives and the only difference was areal density;  but that's never the case.    A 1.5TB drive is generally a 3-platter, 6-head unit;  whereas most 160GB drives are single platter, one sided ... so the areal density of the 1.5TB unit will only be about double that of the smaller drive -- or a bit higher if the 160GB drive is 2-headed.    But in any event, it won't be anywhere near 10 times the speed.
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by:vanauden
ID: 37708483
Wow, I didn't expect so many great answers! Thank you!
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by:vanauden
ID: 37708486
Really great answers, but GaryCase gave the most complete answer. Thank you all!
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by:vanauden
ID: 37708508
Incidentally, GaryCase, I just wanted to respond to your comment that the slowness of a 5400RPM drive could be due to fragmentation. I agree that this is a huge factor when dealing with a well-used/mostly unmaintained (PC), but you also say that 7200rpm is  "only" 1/3rd faster then 7200rpm drives. To me, that is a massive speed increase. 5400RPM drives should simply not be made. Their slowness is ridiculous these days, and most people buying laptops get taken for a ride by manufacturers trying to save money. They probably never realize that one of the reasons that their laptop is slow is due to the fact that it contains a slow drive.

I am preaching to the converted here, I would guess, but that is a huge speed increase when dealing with something like a netbook, don't you agree? I mean, yes you should look at RAM first, but when looking for cheap and "easy" upgrading (well, easy for a techie), the HD is the second thing that I usually look at. Actually, such an upgrade should never happen. People (non-techies) should be buying laptops with 7200RPM HDs and leaving the 5400RPM laptops on the shelf. The manufacturers are taking advantage of their lack of knowledge and saving $10 buck or so per netbook or laptop. That isn't right.

Note: I don't believe that "heat issues" is a good enough reason to use a 5400RPM HD.

Just wanted to put my two cents in for that. Thank you very much for your excellent and very knowledgeable answer.
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by:garycase
ID: 37708559
Agree 1/3rd is a reasonably good increase in performance ... my key point was simply that the interface speed, as long as it's above the sustained data rate of the drive, was essentially irrelevant to performance ... whether it's IDE, SATA, SATA-2, SATA-3, or SAS.

Just how much faster a 7200rpm drive is relative to a 5400rpm unit is a function of a variety of factors => clearly the rotational latency is always 1/3rd better for a 7200rpm unit;  but the sustained data rate is only better if the areal density is the same (or higher) -- in some cases the slower drive will actually have a better sustained transfer rate.   [That's especially true when comparing high capacity "green" drives with older lower capacity drives.]    The seek time is almost always slightly better for a 7200rpm unit (typically 10-20% better).

There are other factors at play as well ==> all modern drives have zoned sectoring, so the outer cylinders have transfer rates nearly double that of the inner cylinders.    So, for example, a high capacity 5400rpm drive with an OS partition structured to reside solely on the outer cylinders will generally outperform a 7200rpm drive that's using the entire drive for the OS.

Bottom line:   I agree 7200rpm drives are better -- and only use 7200rpm drives for system drives;  but I do use slower "green" drives for high capacity backup drives -- and, for example, in my storage server (24TB of fault tolerant storage).    For my Netbook, laptop, and a couple of my HTPCs that I want to boot quickly I use SSDs.    THAT is the best choice for performance -- especially in a Netbook or Notebook where you want not only performance but also low power consumption [A typical SSD draws less than 1/10th the power of a rotating platter drive -- and has 20-30 times better "seek" performance along with 2-5 times the sustained transfer rate :-)
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by:lojk
ID: 37708987
Sorry, how did my answer that was first and contained all relevant information not warrant an assist?
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by:vanauden
ID: 37722897
Hi lojk

I'M sorry about that, but I had to make a choice. I did not want to break up the points too much. The thing is, that I wanted more details on the SATA and RPM technologies and how they interacted with each other. I still appreciated your answer. Truth be told, garycase was the one I wanted to give all the points to, but the other two experts had provided information that he specifically talked about in his post. It was a judgement call.

I'm sorry about that, because I appreciated everyone's help.
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