I know nothing about laptop hard drives

Electro · 05-30-2008, 05:43 PM

Quote:

Higher Rotational speed = Lower Seek time..

Still false. An optical drive keeps on increasing RPM but its accessing times is still the same. Same goes true with hard drives. It is actually the actuator of the hard drive that relates to the accessing time. Also the quality of the magnetic material helps decrease the accessing times. The RPM relates to the sustain rate. Though faster RPM hard drives have to do more ECC compared to slower RPM hard drives.

farslayer · 06-02-2008, 09:57 AM

Now you've switched tracks and are discussing the differences between CLV(Constant Linear Velocity) and CAV (Constant Angular Velocity) in rotational media.. Hard Drives don't vary the spindle speed per the location of the head on the platter, so your comparison is not accurate.

CLV Varies the Speed of the Media so it passes the Read head at the same speed regardless of whether you are reading the innermost track of the optical media or the outside tracks. Used in Optical Drives

CAV spins the drive at a constant speed so the media is passing the head at a much faster rate on the outer edge of the disk than the inner tracks, which is going to cause the data transfer rate to vary based on where the data resides on the disk. CAV is used in Hard disks..

The fact is a drive spinning at 10K RPM will complete one revolution faster than a drive that is spinning 5400 RPM. the media is passing by the drive head at a faster rate on the outer edge of the Disk vs the inner edge of the Disk is going to hold true for all hard drives.

To claim that Higher RPM Hard drives don't have a lower seek time is ludicrous.

http://www.seagate.com/www/en-us/sup...onsiderations/

Quote:

Rotational speed indicates the maximum speed at which the platters can spin to place a particular data storage point under the read/write heads. Rotational speed is determined by the maximum number of revolutions the platters can make in one minute (RPM). Generally, a higher RPM produces a better internal data transfer rate, a lower access time, and better overall drive performance.

http://www.tomshardware.com/reviews/...nce,1557.html#

Quote:

Spindle Speed

A drive's spindle speed in revolutions per minute (RPM) is by far the most important parameter in assessing overall performance. A high spindle speed results in higher platter velocity, which means more data passing the read/write heads. The faster a drive spins, the more data it can deliver or store in a given time frame. But high spindle speeds also have a beneficial impact on access time: as soon as the heads are aligned over a track it usually has to wait until the required sectors pass underneath. Higher spindle speeds reduce this latency, although modern hard drives typically start caching data proactively while waiting for the right sector(s) to pass the heads. Even then the drive might still have to wait for a servo track, which is used to mark the beginning/end of a data track.

I would disagree with your assessment

Electro · 06-02-2008, 06:55 PM

Quote:

Originally Posted by farslayer

Now you've switched tracks and are discussing the differences between CLV(Constant Linear Velocity) and CAV (Constant Angular Velocity) in rotational media.. Hard Drives don't vary the spindle speed per the location of the head on the platter, so your comparison is not accurate.

CLV Varies the Speed of the Media so it passes the Read head at the same speed regardless of whether you are reading the innermost track of the optical media or the outside tracks. Used in Optical Drives

CAV spins the drive at a constant speed so the media is passing the head at a much faster rate on the outer edge of the disk than the inner tracks, which is going to cause the data transfer rate to vary based on where the data resides on the disk. CAV is used in Hard disks..

The fact is a drive spinning at 10K RPM will complete one revolution faster than a drive that is spinning 5400 RPM. the media is passing by the drive head at a faster rate on the outer edge of the Disk vs the inner edge of the Disk is going to hold true for all hard drives.

To claim that Higher RPM Hard drives don't have a lower seek time is ludicrous.

http://www.seagate.com/www/en-us/sup...onsiderations/

http://www.tomshardware.com/reviews/...nce,1557.html#

I would disagree with your assessment

That is what they think. It is much more than that. Optimizing the hard drive correctly and using slower rotation speeds can be done. Manufactures always want people think that faster spindle speeds relates to performance. Hitachi is the king of making their hard drives efficient. Their 7K250 and 7K1000 has a performance (low latency) as good as Western Digital Raptor drives, but are 7200 RPM instead of 10000 RPM. Western Digital is doing the next best way to increase throughput, using smaller platters. If a hard drive company makes a very efficient firmware, uses actuators from hard drives that have 5 ms for an accessing time, use a 7200 RPM motor, and use 2.5 inch platters, the performance will be very good and power consumption will be lower.

I do not care what Seagate thinks because of their problem with manufactures making SSD drives and other problems such as heat and processor resources are too high. Heat ruins the quality of the magnetic material to store data with out corruption.

farslayer · 06-02-2008, 08:34 PM

There are certainly multiple methods of skinning the cat. One obvious way to increase throughput is to increase the density of the data on the platter through technologies such as perpendicular recording (Hitachi)

Two identical 2.5" drives with the same data density technologies and all things being equal other than drive rotational speed, the higher spindle speed drive will have an advantage. I don't dispute that there are multiple approaches to increasing throughput, but I certainly won't write off a Higher spindle speed as a factor when choosing a drive.

Throw a dozen 10K RPM SAS drives in your RAID Array or a dozen 15K RPM Drives in the RAID array for your SQL server, there WILL be a distinctly noticeable performance difference in the SQL serer response times.