Hard Drive Data Recovery - A Basic Understanding of Platter Sizes

Hard disks get their name from the inflexibility of the platters used, as compared to floppy disks or other media which use flexible "platters" (usually, they arent even called platters when the material is flexible). Every hard disk contains one or more flat disks that are used to possess the data in the drive. These disks are called platters also known as disks or discs and are made up of two main substances; a substrate material that comprises the main part of the platter and gives it structure and rigidity, and a magnetic media coating which actually holds the magnetic impulses that correspond to the data. The platters are what it is all about. This is where the data itself is stored. Logically then, the condition of the platters and above all, their media coating, is crucial. The surfaces of all platters are precision machined for accuracy and treated to eliminate any imperfections. The hard disk itself is then put together in a clean room to minimize the chances of any dust or contamination on the platters

The size of the platters is the key factor in determining the hard drives actual physical dimensions. Since most drives are manufactured for use inside a PC they are produced in a number of standard sizes. These standards are called had disk form factors and primarily refer to the drives outside dimensions. Often disks are referred to by a size measurement; i.e. a 3.5 hard disk. When these terms are used it typically refers to the disk's form factor, and usually, the form factor is based upon the platter size. As a general rule, the platter size of the disk is the same for all drives of a given form factor. This is not always true though, especially with the newest drives. Every platter in any specific hard disk has the same diameter.

Today, undoubtedly the most common hard disk platter size in the PC world is 3.5". In reality, the platters inside a 5.25" hard drive are 5.12" in diameter, and those inside a 3.5" hard drive are 3.74". Old habits die hard and the "approximate" names are normally used. You will also notice that these numbers correspond to the common sizes for floppy disks because they were designed to be mounted into the same drive bays in the case. Usually, laptop drives are smaller due to manufacturers' boundless quest for "lighter and smaller". The platters on these drives are usually 2.5" in diameter or less; however, drives with 1.8" or even 1.0" platters are being seen more frequently in mobile equipment.

In order to maximize the amount of storage they can fill on the hard drive, platters are made to stretch as far across the distance of the physical hard drive as possible. However, the overall style is towards smaller platters. It would seem that this may be backwards thinking; after all, bigger platters mean there is more room to store data. Wouldnt it be more cost-effective for manufacturers to produce platters as large as possible? Platter size is shrinking for a number of reasons which are mainly linked to performance. The areal density (the amount of data that can be stored in a given amount of hard disk platter "real estate) of disks is rising so rapidly that the loss of capacity by going to smaller platters is viewed as a non-issue.

Its helpful to understand that just because you hit the Delete button your data is not actually removed from your hard drive. The data clusters remain unaffected however, the files directory location changes to point at the Recycle Bin. Even if you empty your Recycle Bin your data is still accessible. The actual data in the clusters is left intact but the entry for the file in the FAT is changed so those clusters are now free to be used again. This is indicated by the first character of the file name being changed.

Listed below are some of the key factors behind companies are moving toward smaller platters even for desktop units:

----Improved Rigidity: The rigidity of a platter refers to how inflexible it is. Rigid platters have added resistance to shock and vibration. They are a better match for being paired with higher-speed spindles and other high-performing hardware. Reducing the hard disk platter's diameter by a factor of two nearly quadruples its rigidity.

----Manufacturing Ease: The smoothness and evenness of a platter is essential to its quality; an ideal platter is absolutely flat and consistent. Flawed platters lead to a decreased manufacturing yield as well as possible data loss because of the heads coming in contact with uneven areas on the surface of a platter. Smaller platters are easier to make than larger ones.

----Decrease in Mass: Hard disk spindles are escalating in speed providing improved performance. Smaller platters are easier to spin, require less-powerful motors and they come up to speed quicker from a stopped position.

----Power Conservation and Noise/Heat Reduction: The use of power, especially for mobile computing, has always been an issue. Smaller drives commonly use a smaller amount of power compared to larger ones which in turn produces less noise and heat.

----Improved Seek Performance: Decreasing the size of the platters decreases the distance in which the head actuator must move the heads side-to-side performing random seeks thus improving seek time and making random reads/writes more efficient. This is done however, at the cost of capacity. In theory the same performance improvement could be realized on a larger disk by only filling the inner cylinders of each platter. Some people used to partition hard disks and use only a tiny portion of the disk in order to achieve faster seek times. Using a smaller platter size is more efficient and simply easier. The movement to smaller platters began in earnest when some manufacturers "trimmed" the platters in their 10,000 RPM hard disk drives from 3.74" down to 3" while keeping them as standard 3.5" form factor drives on the outside for compatibility. Seagate's Cheetah X15 15,000 RPM drive goes even further, dropping the platter size down to 2.5", again trading performance for capacity (it is "only" 18 GB, less than half the size of modern 3.5" platter-size drives.) This drive, despite having 2.5" platters, still uses the common 3.5" form factor for external mounting (to maintain compatibility with standard cases), muddying the "size" waters to some extent (it's a "3.5-inch drive" but it doesn't have 3.5" platters.) The smallest hard disk platter size obtainable on the market today is a tiny 1" diameter! IBM's amazing Micro drive has a single platter and is designed to fit into digital cameras, personal organizers, and other small equipment. The tiny size of the platters allows the Micro drive to run off battery power, spin down and back up again in less than a second, and withstand shock that would destroy a normal hard disk. The only downside is that its capacity is "only" 340 MB.