How important is RPMs in a modern HDD?

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I'm considering buying a new HDD for backups. I like them to be done when I get up in the morning, so I don't want something exceptionally slow. Seagate has some very affordable multi terbyte BarraCuda drives available, but they're 5400 RPM.

I read recently that HDD RPMs are not as important as they used to be. But there was no documentation provided. I'd appreciate some insight on this from knowledgeable posters. Documentation is appreciated when available.

Thank You!
 
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So you understand that a HDD is made up of platters which store magnetic charges. A "head" hovers above each platter and reads or writes data (reading or writing magnetic charges) to the platter. The head is on an actuator arm which swings in and out, while the platter itself spins. The combination of the spinning platter and swinging actuator makes it possible for the single head to access any portion of the platter.

Here's a more detailed overview if you're interested: http://www.explainthatstuff.com/harddrive.html

In any case, the faster the platter is spinning, i.e. the higher its RPM, then the more of each platter will...
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Hellfire13

Hellfire13

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Documentation is rare but the general idea is, when running active applications or media from the drive, 5400 will show more latency than 7200. As long as you are using it just for back up and not running any active application or media off it, it should be fine if you do not mind the extra time.
 
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rhysiam

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You're leaving the backup running overnight? How will the drives be connected? USB2? USB3? SATA?

Usually for a home backup solution you just get cheap drives.

How much data are you backing up and how long does it have to run before it will annoy/bother you? Just do the maths on how much data you need to transfer per second. For comparison, for a 1TB backup over 8 hours you only need to average just over 35MBps. If your backup includes loads of tiny files that might start to justify a faster disk, but if we're talking majority photos, videos, music, etc, then even cheap drive from 10 years ago can sustain that speed.
 
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James Mason

James Mason

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In terms of Read and Write speeds, yeah the RPMs do effect the reading and writing of data.
Speeds below 7200 rpm also can have negative application performance, but well SSDs also improve application performance.
But SSD prices per GB are dropping enough that the higher RPMs of 10k and 15k for magnetic HDDs are no longer a good price/speed/storage compromise.

7200 and above = good for OS and applications
7199 and below = good for storage of infrequently accessed data.
 
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rhysiam

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Well then don't waste money on a faster drive. USB2 maxes out at around 40-45MBps real world transfer rates.
 
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I'm not familiar with MegaBytesPerSecond versus RevolutionsPerMinute, how do they compare?

Thanks!
 
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Hellfire13

Hellfire13

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The faster the RPM, the faster the disk will spin, creating faster read/write in terms of mbps. Thats the relation/comparison.
 
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rhysiam

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So you understand that a HDD is made up of platters which store magnetic charges. A "head" hovers above each platter and reads or writes data (reading or writing magnetic charges) to the platter. The head is on an actuator arm which swings in and out, while the platter itself spins. The combination of the spinning platter and swinging actuator makes it possible for the single head to access any portion of the platter.

Here's a more detailed overview if you're interested: http://www.explainthatstuff.com/harddrive.html

In any case, the faster the platter is spinning, i.e. the higher its RPM, then the more of each platter will be passing under the drive head per second, potentially allowing the drive to read and write data more quickly.

The relationship between RPM and MBps is really only a general one. Different drives have different density, as in they store more (or less) data in the same area. So a slower spinning drive with higher density may still be able to read and write faster. The number of platters can also vary, the amount of cache, etc, etc. All these things can impact on drive speed too. So a 7200RPM drive is not necessarily faster than a 5400RPM one. It's a particularly poor metric if you're comparing old vs new drives.
If you're only comparing new drives, it is actually fairly representative though. That's primarily because faster RPM drives tend to be a little more complex (= more expensive) to produce and are less power efficient. For that reason the 7200RPM drives are usually engineered from the ground up to be the higher spec, better performing and more expensive drives.

There's no question though that if you're connecting it to a USB2 interface, just get a cheap drive and be done with it.
 
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