Articles: Storage

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Our customary practice is to review hard disk drives of the same or similar storage capacity but this review is an exception. We will compare products that differ as much as twofold in terms of storage space. Why? We have just happened to obtain HDDs with new platters. 333GB 3.5-inch platters used to be the largest in the last year, but newer HDDs come with 375GB or even 500GB platters. Of course, there are but few such products available as yet, so we can only compare them to their predecessors. This will show us what benefits we can achieve from the transition to such a high recording density.

If you know the history of CPUs well enough, you should be aware that a transition to a thinner manufacturing process is often accompanied with a bunch of other changes. With CPUs, it had transpired some time ago that reducing the size of a transistor would not be enough to increase CPU clock rates further because the leakage currents had got too high. As a result, the CPU makers had to master not only new methods of lithography (or revise old ones) but also introduce new technologies to improve the insulation of the semiconductor structures from the wafer.

It is the same with HDDs. When the recording density is increased, each magnetic domain takes a smaller area on the platter surface. As a consequence, there arise problems with reading and writing because the heads have to fly very close to the platter and be very sensitive in order to work with such very small domains. And if the platter rotation speed remains the same, the clock rate of the head’s electronics must be increased because the head will spend less time over each domain. A reduction in the domain width makes it harder for the heads to find the necessary domain. And when the head flight height is reduced, the HDD becomes more sensitive to spindle misalignments, platter vibrations and other things that may result in the head just hitting the platter surface on the outermost or innermost tracks with all the ensuing consequences. Thus, the release of HDDs with higher-density platters should be credited not only to the platter makers but also to the suppliers of all the other components.

So, 333GB platters are not the top of the range anymore. 375GB platters made but a short appearance: the growth of the recording density was not big enough to interest the manufacturers. They were preparing for 500GB platters instead: the 50% growth in recording density was a very good objective. It would allow to create absolutely new models: 1TB drives with two platters and 2TB drives with four platters. And now we’ve got such products in our hands. Perhaps they are not perfect but they are the first to come up. The companies that have released them to the market may get some profit by simply offering what the competitors do not have.

Before describing the products, we want to mention the new capacity threshold problem. The last time this problem was encountered when a new addressing method was required in order to overcome the maximum capacity of 127 gigabytes. That was quite a long time ago and could be solved by updating mainboards’ BIOSes. The current problem is of a different nature. The fact is that the maximum size of a partition in the Master Boot Record (the standard method of Windows XP to partition a hard disk) that can be formatted and made a system partition is 2TB sharp. According to the HDD makers’ reckoning 2 terabytes equals 2 trillion (10 to the power of 12) bytes rather than 2 to the power of 41 as OSes think. The latter number is somewhat bigger, so the current HDDs are free from that problem. But if Hitachi returns to a 5-platter design once again and uses 500GB platters, the resulting HDD will be far larger than 2 terabytes and you won’t be able to create a Windows XP partition with the maximum capacity on it.

Of course, this problem is not a disaster. You can (and, in our opinion, even should) create multiple partitions if you’ve got one HDD in your system. And on the other hand, Windows Vista and 64-bit Windows XP support GPT (GUID Partition Table), a different format of a disk partition table that is free from the above-mentioned limitations. But you should be aware that booting Windows from a GPT partition is only possible if your system uses EFI, the new type of the system loader that is going to replace the traditional BIOS. In fact, if your OS is installed on a HDD with an MBR, you can add disks with GPT partitions to it as users usually do when they have RAID controllers with large partitions (2-terabyte partitions are quite a common thing with RAIDs); EFI is only necessary to boot from such disks.

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