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SATA speeds, Disk RPM's - Difference

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February 3, 2011 7:29:56 AM

Am looking to buy hard disk, and there are factors like SATA II (3 Gbps), SATA III (6 Gbps).....and then we have Disk RPM's as 5400, 7000, 10000.

what do these two factors mean? is one dependent on other?
how would i determine which is faster when two factors come into picture?
a b G Storage
February 3, 2011 10:33:18 AM

Before getting started, ensure that you have a motherboard in your system that supports SATA 6. Chances are that unless it is basically a brand new motherboard, it will not have the latest SATA connectivity, but rather SATA II. So don't waste the additional money on a SATA 6 capable HDD.
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a c 371 G Storage
February 3, 2011 11:03:05 AM

SATA 1 (1.5g/s), SATA 2 (3g/s) and SATA 3 (6g/s) is the interface speed - how fast data can be transferred between the computer and hard drive. These are maximum speeds. A drive can be SATA 2 and not reach it's full speed.

5400, 7200, and 10,000 are the drive's platter speeds in RPM's. The faster the disk spins, the faster it can read/write to the disk.

Most mechanical drives today should be SATA 2 since most don't come close to the 3g/s maximum limit. SATA 3 is best used for SSD's (solid state drives). 7200rpm is pretty much standard on today's desktop drives. 5400rpm is mostly used in laptop drives and green drives.

For most desktop needs, a 7200rpm SATA 2 drive is sufficient.
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February 4, 2011 2:42:32 AM

buwish said:
Before getting started, ensure that you have a motherboard in your system that supports SATA 6. Chances are that unless it is basically a brand new motherboard, it will not have the latest SATA connectivity, but rather SATA II. So don't waste the additional money on a SATA 6 capable HDD.


my bad...i failed to mention am upgrading my pc completely.. and that the hard disk was just a small part of it :D 
i was exploring the sandy bridge option until the recall...so wil wait for a chipset to come out and of course wait for 2 more months after that :sarcastic: 

there is one thing i have noticed in newer motherboards, they have only a couple of 6 Gbps ports and remaining are 3 Gbps. Why dosent it completely support 6? Is 6 not backwards compatible with 3 or something?
See this -> P8P67

Also there are like 4 USB 3.0 ports & 12 USB 2.0 ports. If 4 ports can be 3.0 why not let all support the higher speed version?

Are these a limitation of the chipset or motherboard?
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February 4, 2011 3:17:08 AM

Hawkeye22 said:
...A drive can be SATA 2 and not reach it's full speed.

Most mechanical drives today should be SATA 2 since most don't come close to the 3g/s maximum limit. SATA 3 is best used for SSD's (solid state drives). 7200rpm is pretty much standard on today's desktop drives. 5400rpm is mostly used in laptop drives and green drives.

For most desktop needs, a 7200rpm SATA 2 drive is sufficient.


I was reading a bit about this on wiki Hard Disk -> Data transfer rate. The SATA 2 which is 3 Gbps -> 3072 Mbps -> ~375 MBps, is basically the buffer to computer rate. But the disk to buffer can achieve max of 1030Mbps -> ~130MBps speeds. Other links specified 70 MBps as max. So basically it dosent make a difference between SATA 2 or SATA 3 as it is limited by the disk to buffer speeds.
I guess this is what you meant by, A drive can be SATA 2 and not reach it's full speed.

So my questions..
1. Would it make a difference from 7200 RPM to 10000 RPM? Dooes the RPM speeds directly translate to the disk to buffer speeds...does Faster RPM mean faster from disk to buffer?
2. If yes, what rates can 10000 RPM achieve.
3. Is this where the solid state drive have the advantage in terms of speeds? The 'storage' to buffer rates?
4. If yes, what rates do they achieve?

Anyways my buying a PC will be delayed by about 4-5 months i guess. Hopefully i shall see a price drop in SSD's by then :sarcastic: 
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a c 167 G Storage
February 4, 2011 3:23:19 AM

The sata speed is the maximum rate that data from a hard drive's buffer can be transferred across the interface. This is really a non issue for hard drives because no conventional hard drives can saturate even the sata 1 bus.

Very little data is likely to be found in the hard drive buffer. The rpm of the hard drive determines part of the access time. Faster rpm reduces the time a drive waits until the requested data comes under the read/write heads. Contrary to popular opinion, faster rpm does not usually result in a faster data transfer rate. Faster data rates come more from denser platters, and accessing the longer outer cylinters of the drive.

Bottom line is that there is not a heck of a lot of difference in performance among the whole range of hard drives.

The real difference comes with a solid state drive(SSD). There is no mechanical motion, so access time is negligible. Data transfer times are equal, and usually much better.
It is for SSD's that you might need the 6gb data transfer rate of sata 3. It would be unusual to get more than 2 ssd's, hence only 2 6gb sata ports are typiical.
For hard drives and dvd's 3gb is twice the capability that you need.

USB3.0 is new, and much faster. I imagine it is also a bit more expensive. For now, you will not usually see someone using more than 2 high speed external device.

The chipset provides some things. In the case of P67, for example, you get (if I remember correctly)2 6gb sata, 4 3gb sata, and 14 usb2.0.
Motherboard vendors may add more sata ports, usb3.0 ports and other attachments that they think is needed in the marketplace.


I strongly support SSD's for the os and apps. They truly make a difference. Larger SSD's will usually be faster. Put it on a 6gb port, and specify sata mode = AHCI(not ide or raid) to get trim support.
If you need more, gat a hard drive for overflow and storage. For backup, get a external drive with a usb3.0 interface. I think it is easier than e-sata which should also work.


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a c 371 G Storage
February 4, 2011 10:54:57 AM

ohshaq said:
I was reading a bit about this on wiki Hard Disk -> Data transfer rate. The SATA 2 which is 3 Gbps -> 3072 Mbps -> ~375 MBps, is basically the buffer to computer rate. But the disk to buffer can achieve max of 1030Mbps -> ~130MBps speeds. Other links specified 70 MBps as max. So basically it dosent make a difference between SATA 2 or SATA 3 as it is limited by the disk to buffer speeds.
I guess this is what you meant by, A drive can be SATA 2 and not reach it's full speed.

So my questions..
1. Would it make a difference from 7200 RPM to 10000 RPM? Dooes the RPM speeds directly translate to the disk to buffer speeds...does Faster RPM mean faster from disk to buffer?
2. If yes, what rates can 10000 RPM achieve.
3. Is this where the solid state drive have the advantage in terms of speeds? The 'storage' to buffer rates?
4. If yes, what rates do they achieve?

Anyways my buying a PC will be delayed by about 4-5 months i guess. Hopefully i shall see a price drop in SSD's by then :sarcastic: 


I know this was directed at me, but I feel that geofelt answered this adaquately.

To sum it up...
faster RPM's = lower latency
SSD = extremely low latency and faster transfer rates as there is no spinning platter.
SATA is built into the southbridge, but some ports can be on an additional 3rd party chip (JMicron).

SATA3 & USB3 are still fairly new. When more SATA3 and USB3 devices are on the market I'm sure you will see more ports added to the motherboard.
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a c 167 G Storage
February 4, 2011 1:11:06 PM

ohshaq said:
I was reading a bit about this on wiki Hard Disk -> Data transfer rate. The SATA 2 which is 3 Gbps -> 3072 Mbps -> ~375 MBps, is basically the buffer to computer rate. But the disk to buffer can achieve max of 1030Mbps -> ~130MBps speeds. Other links specified 70 MBps as max. So basically it dosent make a difference between SATA 2 or SATA 3 as it is limited by the disk to buffer speeds.
I guess this is what you meant by, A drive can be SATA 2 and not reach it's full speed.

So my questions..
1. Would it make a difference from 7200 RPM to 10000 RPM? Dooes the RPM speeds directly translate to the disk to buffer speeds...does Faster RPM mean faster from disk to buffer?
2. If yes, what rates can 10000 RPM achieve.
3. Is this where the solid state drive have the advantage in terms of speeds? The 'storage' to buffer rates?
4. If yes, what rates do they achieve?

Anyways my buying a PC will be delayed by about 4-5 months i guess. Hopefully i shall see a price drop in SSD's by then :sarcastic: 

1. There is a small difference in performance between 7200 10k or 15k drives. RPM does not translate directly to disk to buffer speeds. The density matters more.
2. A 10k drive will have shorter seek or positioning times, and will be a bit faster for short random reads. That is what the os does mostly.
3. Yes; this is exactly why a SSD is great for the OS.
4. A hard drive will have 3-4ms average access time. It will transfer data at perhaps 100 - 150 MB/sec.
A SSD will have a 0.1 ms access time. Data transfer rates will be on the order of 200MB/sec.
Gen3 SSD's will be out soon, and the transfer rates will double.
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February 7, 2011 4:46:11 AM

Best answer selected by ohshaq.
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