Hard drive performance RPMs vs GB/s - Which matters more?

[teknix360]

What would be the performance differences between a 3.0GB/s 7200 RPM hard drive and 6.0GB/s 5400 RPM hard drive?

I'm not really clear on how spin or write speeds affect performance, other than faster is better. I'm especially curious about performance in this example since it's not an apples to apples comparison. Does the higher transfer rate always win out?

Also how does cache size come into play?

[Vice]

Neither. You need to look at benchmarks of the actual drives. Some websites such as Toms Hardware benchmark drives.

The reason I say this is because many different factors play in to the performance of a drive. Areal Density, Platter Size, Cache, Rotational Speed, Access Latency, Connectivity and OEM specific optimisations in the way data is queued and accessed.

Simply comparing drives on RPM speed is not accurate as I could show you 5,200 RPM drives that beat 7,200 RPM drives or even 15,000 RPM drives. You really have to compare each drive in real benchmarks and not just the specifications listed on a shopping site.

[ViperAFK]

What would be the performance differences between a 3.0GB/s 7200 RPM hard drive and 6.0GB/s 5400 RPM hard drive?

I'm not really clear on how spin or write speeds affect performance, other than faster is better. I'm especially curious about performance in this example since it's not an apples to apples comparison. Does the higher transfer rate always win out?

Also how does cache size come into play?

You are confusing SATA speeds with the speeds of the drives themselves. The 7200RPM drive will be faster in every way. No mechanical hard drive can even saturate sata 3.0 GB/s

[teknix360]

No mechanical hard drive can even saturate sata 3.0 GB/s

Interesting. So why are there 6.0GB/s mechanical drives? Is it just a marketing ploy?

[Scorpus Veteran]

Interesting. So why are there 6.0GB/s mechanical drives? Is it just a marketing ploy?

Essentially. It's also probably due to the manufacturers wanting to keep up with modern standards, such as how some low-end graphics cards support PCIe 2.0 but don't even saturate the bandwidth available in PCIe 1.1

[wahoospa]

Doesn't GB/s make a big difference? I have 2 laptops and both came with sata 1.5GB/s 5400 rpm hard drives.

I replaced them with the same size hard drivers but with 3.0 GB/s sata hard drives. My Windows Experience for hard drives went up 1.1 points.

[Vice]

Interesting. So why are there 6.0GB/s mechanical drives? Is it just a marketing ploy?

SATA 3 isn't just about speed although that is the main noticeable difference. For example it features Improved Power Management and new operating system level NCQ management and the newer NCQ Isochronous mode which makes it better for delivering low, medium and high bitrate content like High Definition video without interruptions or stalling while seeking for content bits on the disk.

In short SATA 3 is an overall improvement of the standard and much like SATA 2 (which brought hot-plugging, NCQ, eSATA etc) SATA 3 continues that trend of improving the overall feature set whilst also doubling the data rate. This is the reason you'll find it adopted on Hard Disks that will never even come close to saturating the 6.0Gb/ps link it provides.

[pupdawg21]

The 3Gb/s vs 6Gb/s makes little difference on most SATA hard drives because as others have said since almost none of them can even max out a 3Gb/sec link. This is just the maximum theoretical speed that data can be transferred between the system and the hard drives internal cache. This is not the rate as which a drive can actually write data to its' platters. In most cases a drive with a higher RPM will be faster than 1 with a slower RPM under most circumstances. A drive with a higher platter density with a lower RPM vs a drive with a higher RPM (The lower rpm can win) but lower density may perform slower under certain situations because (the higher rpm drive) has to move its heads a greater distance to address the same amount of data. But all things being equal if the density of the platters are the same between the 2 drives the one with the higher RPM will normally win regardless if its connected via 3Gb/s or 6Gb/s when it comes to mechanical drives.

There are many exceptions to this since some manufacturers do extra optimizations in firmware and cache to inch better bursty performance for brief periods of times but not sustained.

[PGHammer]

Essentially. It's also probably due to the manufacturers wanting to keep up with modern standards, such as how some low-end graphics cards support PCIe 2.0 but don't even saturate the bandwidth available in PCIe 1.1

In the case of hard drives and GPUs, it's more current standards than anything else - a sample case in GPUs is the notebook-in-desktop-clothes AMD HD5450 and HD6450; despite neither even coming close to saturating PCIe 2.0, I don't know of any that aren't shipping - in any guise - as less than PCIe 2.1 parts.

A rather interesting case in hard drives are the Caviar Eco-Green series of SATA 3.0g/second hard drives - while they have much higher capacities, they aren't much faster in terms of transfer rates as the SATA-150 HDDs of 2005/2005 vintage.

The first (of two) Caviar Eco-Greens I've used as boot drives replaced, in fact, a Maxtor DiamondMax of that ancient (in SATA terms) SATA-150 speed - that 500GB (465GB NTFS-formatted capacity) drive is now Mom's boot drive.

Meanwhile, I have a 1TB (931GB formatted capacity - also NTFS) Eco-Green boot drive - the only reasons it comes closer to the transfer-rate ceiling are the 32 MB on-drive cache and the higher areal density.

[Jason S. Global Moderator]

can i just point out that the SATA standards are NOT in gigabytes per second... it's gigaBITS per second. the SATA2 standard is 3Gb/s which is a theoretical maximum - so it's not even practical or likely in the real world. also, this 3Gb/s is NOT the speed of the hard drive. hard drives are MUCH slower. the SATA spec is just the transfer mechanism.

[Astra.Xtreme]

SATA spec is beneficial when talking about SSD's since 3Gb/s and 6Gb/s will have a substantial difference.

With mechanical HDD's, as others have said, it's just a marketing term to keep up with modern standards. On a HDD, 3Gb/s compared to 6Gb/s is nil.

[Roger H. Veteran]

Doesn't GB/s make a big difference? I have 2 laptops and both came with sata 1.5GB/s 5400 rpm hard drives.

I replaced them with the same size hard drivers but with 3.0 GB/s sata hard drives. My Windows Experience for hard drives went up 1.1 points.

You probably replaced them with newer drives which are inherently faster. You probably got a bigger drive as well which might just have a higher aerial density as well.

So to your original question - when buying HDDs, SATA2 vs 3 almost doesn't matter - spend on buying a bigger drive even if you don't really need the space as aerial density will give you a nice boost.

[chconline Veteran]

Doesn't GB/s make a big difference? I have 2 laptops and both came with sata 1.5GB/s 5400 rpm hard drives.

I replaced them with the same size hard drivers but with 3.0 GB/s sata hard drives. My Windows Experience for hard drives went up 1.1 points.

It's because you bought a newer, faster drive, probably with higher areal density, not because of a faster interface.

[2xSilverKnight]

If you want real speed, it's a sata3 SSD or nothing.

[teknix360]

Wow, thanks for all the information! I didn't know that modern drives aren't able to fully hit the 3.0 GB/s mark. I think I have a better understanding of what all the specs actually mean in the real world.

Since someone brought up SSDs... you would notice a performance difference in 3.0 vs 6.0 GB/s solid state drive? Mostly in transferring files or actual system performance?

[Roger H. Veteran]

Wow, thanks for all the information! I didn't know that modern drives aren't able to fully hit the 3.0 GB/s mark. I think I have a better understanding of what all the specs actually mean in the real world.

Since someone brought up SSDs... you would notice a performance difference in 3.0 vs 6.0 GB/s solid state drive? Mostly in transferring files or actual system performance?

3Gbps is about 370MB/s which was the limiting factor in SSDs before the 6Gpbs ones came out. Remember, lower case b, not upper case as you keep writting it above :D. So 6Gbps is the new ones, the limit for those is 750MB/s which is why we have SSD now pushing 550MB/s.

So if you get a 3Gbps SSD you wont see much difference for opening Browser or Microsoft Office applications when compared to a 6Gbps SSD. If you are doing transfering of files or video editing they say then you'll see a diff.

NOTE - The above are theoretical limits so minus some for "real world" speeds. Example SATA2 has a 3Gbps max but in reality it's about 2.4Gbps max which then leaves you at 300MB/s max possible. Same goes for SATA3 in that it will never attain full speeds.

[chconline Veteran]

Wow, thanks for all the information! I didn't know that modern drives aren't able to fully hit the 3.0 GB/s mark. I think I have a better understanding of what all the specs actually mean in the real world.

Since someone brought up SSDs... you would notice a performance difference in 3.0 vs 6.0 GB/s solid state drive? Mostly in transferring files or actual system performance?

Firstly, I'd highly recommend you to fix up your conventions. Capital B is "byte". Lower case b is "bit". 1 byte = 8 bits. It's not the same thing.

85% of the time you won't notice a difference from a SATA 3Gb/s SF-1222 to a SATA 6Gb/s SF-2281 drive, since it's so fast already -- but faster the better :p (SSDs I've owned or currently own: OCZ Vertex 2 60GB, OCZ Vertex 2 160GB, G.Skill Phoenix EVO 115GB - SATA 3Gb/s; OCZ Vertex 3 Max IOPS 240GB, OCZ Agility 3 240GB, Patriot Pyro 120GB, Patriot Pyro SE 240GB, Kingston HyperX 120GB - SATA 6Gb/s).