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HDD Storage mechanics

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July 4, 2011 1:41:29 AM

I'm looking for advice on HDD mechanics, specifically HDD performance.

Now as we all know, HDD has a few important specs: RPM, capacity, cache, and maybe platter count. I think all of these contribute to performance.

Now what I'd like to know is: Does higher capacity + slower RPM = high RPM + lower capacity? Something like that.

For example: Would a 5.9k RPM 2TB drive perform better than a 7200RPM 640GB drive, simply because the bit density is much greater?

More about : hdd storage mechanics

a c 104 G Storage
July 4, 2011 6:04:10 PM

Hello,

Lot goes into HDD performance, and the engineers are continually working on how to make them faster.

Hard disks are set up with platters, and each platter has tracks (divided into segments or clusters.) Multiple platters can be accessed on both sides, and the same track position vertically on multiple platters form a cylinder (track x 2 x #platters) each side of which has a read/write head which can be used 'almost' simutanteously. And of course, how tightly packed the bits are on each track determines how rapidly each can be written to sequentially.

So, rotational speed of the platters, the number of platters, the bit density, track to track head positioning time (latency), sequential or random access all play a roll in performance. Because of the moving parts, even RAID-0 multiple disks reach a peak performance at about 5 disks.

The cache (temporary data storage before writing to the disk or holding disk data that probably will be needed next) is important up to a point, and probably is optimal at this time about 32 MB.

The capacity is not a factor in performance, since it determines how much data can be stored, rather than how fast it can be accessed.

You can measure disk performance (speed) with appl programs like HD Tune, I/O meter, Crystal DiskMark to compare one to another.

The biggest factor in disk performance is eliminating the inirtia of all the moving parts (the read/write heads, platters, spindle, etc) which is where the SSD (solid state drives) with no moving parts is making such a hugh impact.

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July 5, 2011 1:12:03 AM

John_VanKirk said:
Hello,

Lot goes into HDD performance, and the engineers are continually working on how to make them faster.

Hard disks are set up with platters, and each platter has tracks (divided into segments or clusters.) Multiple platters can be accessed on both sides, and the same track position vertically on multiple platters form a cylinder (track x 2 x #platters) each side of which has a read/write head which can be used 'almost' simutanteously. And of course, how tightly packed the bits are on each track determines how rapidly each can be written to sequentially.

So, rotational speed of the platters, the number of platters, the bit density, track to track head positioning time (latency), sequential or random access all play a roll in performance. Because of the moving parts, even RAID-0 multiple disks reach a peak performance at about 5 disks.

The cache (temporary data storage before writing to the disk or holding disk data that probably will be needed next) is important up to a point, and probably is optimal at this time about 32 MB.

The capacity is not a factor in performance, since it determines how much data can be stored, rather than how fast it can be accessed.

You can measure disk performance (speed) with appl programs like HD Tune, I/O meter, Crystal DiskMark to compare one to another.

The biggest factor in disk performance is eliminating the inirtia of all the moving parts (the read/write heads, platters, spindle, etc) which is where the SSD (solid state drives) with no moving parts is making such a hugh impact.


But wouldn't higher capacity at the same form factor/platter count implies higher bit density --> higher performance? That is what I am wondering.


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