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7200 RPM Drive Max Byte/Sec?

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December 24, 2008 3:01:15 AM

I was just wondering with all the promotion os 3.0 Gb/s SATA drives, 15000 RPM Drives, and all that, with a 7200 RPM Drive, what is the max Byte (or Bit) per second you can get? Does it depend on other factors? If I have a SATA Drive that touts 3.0 Gb/s (as with most newer SATA connections), can I really get that, or is there a bottleneck in drive read/write speed? Kind of theoretical question, but I would just like to know what the factors are that contribute to my data transfer rates. Thanks!

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a b G Storage
December 24, 2008 3:45:19 AM

The benchmark you should care about most is the average read/write rate. That's what matters when loading a big game level or a video for example.

WD5000AAKS (500GB) gets about 70 MB/s
WD6400AAKS (640GB) about 90 MB/s (you can notice the difference when editing videos - I have both in my PC)
WD Velociraptor or Samsung Spinpoint F1 1TB - close to 120 MB/s

The maximum rates are higher, of course, but they are not sustained so the don't really matter IMO.

The factors that contribute:

1. bit density. The best disks available have 332 GB or even 375 GB platters, with bits packed very close together. That allows the heads to read/write more bits during the same number of rotations. When comparing two 7200rpm disks and reading/writing huge files, bit density is all that really matters.

2. the time needed to move the heads to the right track. Modern disks have smart mechanisms that minimize this type of movement.

3. rpm - this decides the time needed to move the right sector under the heads


The 3.0 GB/s is theoretical, i.e. the limit of the port on the MB. It's nowhere near reached by hard disks. Maybe Flash-based SSDs will eventually reach that limit - one can always hope.
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a b G Storage
December 24, 2008 5:37:57 AM

It is highly drive-specific, but the best current 7200RPM ones can reach around 115 MB/s or so (specifically, the Seagate 1.5TB Barracudas, the WD Caviar Black 1 TB drives, and similar current gen 1TB drives). Another factor that matters is access time - this is fairly similar for most 7200RPM drives though. This significantly drops as rotation speed goes up though, and this is the biggest benefit of 10krpm or 15krpm drives.
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December 24, 2008 6:01:17 AM

sata 3.0 Gigabits/sec gives around an interface bandwidth of 300 megabytes/sec. a single drive using SATA that i know that can come close to that bandwidth are intel SSD drives,over 200 MB/s.

using a 7200rpm drive, you don't have to bother with interface speeds since performance is maxed out around 120MB/s.
denser HD platters in the future will only improve only in a small amount.
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a b G Storage
December 24, 2008 6:27:35 AM

I would say that there is more than just a small amount of improvement coming in HDDs. I wouldn't be surprised to see >2TB hard drives with >150MB/s sequential data rates coming out in not too long.
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