Tuesday, January 4, 2011

(Assembled is a series in which The Indian Geek will be looking at how to choose the components for assembling your own home Desktop PC, over the course of a few weeks. This week's article is about selecting a Hard Drive. Also, check out our articles on choosing the right CPU and graphics card)

Hard Drive

This week we’re going to talk about what to look for when buying a hard drive. Most people, and even computer manufacturers, describe a hard drive by only its capacity. While capacity is a big factor, there’s a lot more to a hard drive. A hard drive plays a key role in a computer’s general performance and speed. Even with the fastest CPU and RAM available, if the hard drive is going to feed them data byte by byte, the PC would only let you stare at a spinning hourglass. In this article, we’re going to briefly look at four factors that could make a difference in your hard drive, and then decide on which hard drive you should select, based on your budget and required performance.

If you’re a full-fledged geek, you already know how a hard drive works. If you aren’t, no need to sweat - we found a Youtube video which briefly depicts the parts of a standard computer hard drive, and explains it. So now, you can show off too.


Read speed - The maximum speed at which the drive is able to read data sequentially. However, this cannot be reached in normal computer use. This speed is possible when reading large files that are stored in one spot on your hard drive’s discs (platter). Since files are generally fragmented and stored in pieces all over the hard drive, the sequential read speed does not affect everyday hard drive performance much. You could compare this to reading a novel where the text is continuous and flowing.


Write speed - Similar to sequential read speed, but for writing (or storing) data to the hard drive. It will be slower than the read speed, since just like us, humans, hard drives are faster at reading than writing.


Access time - This is the time a hard drive takes to jump back and forth between data that’s spread out across its platters. This greatly affects performance when a large number of smaller files are accessed like when your operating system is loading or when applications are run. Think of your hard drive as a dictionary, and you need to find a whole bunch of words. Even if you are a fast reader, its not going to help if you cannot turn the pages of the Dictionary quickly enough to find each word and jump to the next word, fast.


Capacity - The most well known parameter. Bigger is better. Trust us when we say, you can never have too much space. You’ll always find someway or the other to fill it. With all forms of digital media taking on higher-capacity storage formats (FLAC for audio, RAW for digital images, AVCHD for video) you will need all the hard drive space you can get. Buy the biggest drive you can afford while still keeping the above three parameters in mind. Something you might want to keep in mind is that your computer will always report that your hard drive is slightly smaller than the label suggests. Your computer will say your 500GB drive only has 465GB or a 1 TB Hard Drive has only 931 GB of space. Fear not, you have not been robbed. This is because of the way KB, MB and GBs are calculated. Hard drive manufacturers consider 1 KB as 1000 Bytes, 1 MB as 1000 KB and 1 GB as 1000 MB. Thus a 500 GB hard drive has 500,000,000,000 Bytes. Your operating system on the other hand counts 1 KB as 1024 Bytes (210), 1 MB as 1024 KB and 1 GB as 1024 MB. Thus 500,000,000,000 Bytes equates to only 465 GB. Though 24 is a small number, it multiplies as drives get bigger.

With the basics out of the way, let’s look at how to actually select and choose a specific hard drive to purchase for your very own Assembled PC. We are going to divide hard drives into three categories based on the need - storage, performance and balanced.

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Let us start with the balanced category. If you want to have just a single drive that’s fast enough to run your OS as well as big enough to store all your data, we suggest a 7200 rpm drive. These drives offer decent performance as well as a reasonable cost per GB value. They range from 70-100 MB/s when reading/writing data and about 12-14 ms access times. High performance versions like the Western Digital Black series of hard drives are around the upper end of this range, while more budget oriented ones like the Hitachi Deskstar are at the lower end. Our suggestion would be to go for a mid-range 1 TB drive like the Samsung Spinpoint F1 or the Seagate Barracuda. Please keep in mind though that bigger capacity drives will perform better than identical lower capacity drives. This is because the data on the drive platters is more dense and closely packed. Having additional platters will also help. A 2TB 5400rpm drive might outperform a 1TB 7200rpm drive. So it all comes down to what your budget is and what is available out there when you actually walk to the store.

Let’s look at the storage category now. If you just want a large capacity hard drive to store your videos, photos and music, you don’t need a fast drive. Instead, we would suggest that you use the money to buy a larger drive. These drives typically run at 5400 rpm, though some run at 5900 rpm. These have the lowest cost per GB rate and currently go upto 3 TB. Since they spin slower, they also consume less power. While these drives spin slow, if you buy a larger capacity drive (>1TB), they will still perform quite well. However, in general, we would not suggest installing your operating system on a 5400rpm drive. The access time of such drives is typically 15-17 ms and 60-70 MB/s read/write performance. They are best suited for just storage, such as a secondary drive to store all your digital photos and holiday videos.

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Finally, let’s see what high performance drives are out there. If you want high end performance and have Rs. 10,000/- ready to spend on storage for your PC, read on. Western Digital’s Velociraptor is the only traditional hard drive in this category. It spins at a screaming 10,000 rpm with a blazing 7ms access time. Sadly, these drives are very expense. The 600 GB version costs over Rs. 18,000/- At this price point, they are just not worth the money. Unless you get the largest 600 GB version, they’re not going to be big enough for the average user, which means you will need to get a second hard drive. While they are noticeably faster than 7200 rpm drives, they are not as fast as Solid State Drives (SSDs). Solid State Drive Solid State Drives have no moving parts, no magnetic platters and no reading heads. This makes them fast and reliable. They have access times around 0.1 - 0.2 ms. Some go down to even 0.07 ms. That’s almost 250 times faster than a 5400 rpm drive! Read/write speeds are usually in the 100-300 MB/s range. However, SSDs are very expensive. A 200 GB OCZ Vertex 2 SSD costs almost Rs. 35,000/- However, smaller slower SSDs are considerably cheaper. Our suggestion would be to go for one of the budget models like the Solidata K6 or the Kingston SSDnow. A 30-60GB drive should cost you about Rs. 5,000. This would be an ideal drive to install your Operating System and frequently used applications. You will also require a second hard drive for storage. A large 5400 rpm drive will be a good choice for this.


We’d like to round off this article by mentioning a few more options and things to keep in mind.


External USB drives - These come in handy if you want portability or if you have a laptop and want additional storage space. These typically just have a 5400rpm drive in them. They’re slower and meant for storage. Avoid installing/running software from these drives.

RAID - This is a feature that almost every modern computer has, but is rarely used in home computers. RAID an acronym for Redundant Array of Independent Disks. Simply put, it lets you use 2 or more drives for increased performance or reliability of data, in event of hard drive failure. The most common types are 0 and 1. RAID 0 also known as striping increases performance. It treats two identical drives as one large drive. Thus when anything is read or written, half goes on one drive and the half on the other. This increases performance since two are doing the work of one. On the downside, if one drive fails, all is lost since the other half is useless. Two 500GB hard drives in RAID 0 may not cost more than a single 1TB drive and will provide much better performance. If you are willing to risk data loss and other complications involved, RAID 0 is a good way to go. RAID 1 or mirroring is purely for backup. An extra copy of everything is written to a second drive. Thus you have a mirror copy of everything. If there is a failure or corruption in one drive, the system will automatically access it from the copy. Performance may take a minor hit, since every piece of data is written twice. There are several other types of RAID setups using many drives, though these are seldom used for home computers.

Partitioning - Partitioning your hard drive is crucial. While its a post-purchase option, we think its important enough to mention in this article. How a hard drive is partitioned could affect its performance, data security and help or deter the organization of files and folders on the drive. Partitioning divides your hard drive into physical portions of its platters/discs. We suggest that you limit the size of your first partition (<200GB; the smaller, the better) and install your operating system in it. This confines all the system files into one small portion in the beginning of your drive. By having all these files in one spot means your hard drive spends less time going back and forth trying to access them. The beginning portion of your hard drive is also the fastest. We also recommend keeping all your personal files, music, and pretty much everything important on a separate partition. That way if your operating system fails and you need to format your C drive, you personal files will be safe.


So there you have it. We trust this will help you choose a good hard drive. For most users, a 7200rpm drive is the best bet. But if you want something faster or bigger, there are options - just decide on what your computer needs, then head out to your friendly neighbourhood computer store, and buy the hard drive of your dreams. It’s that simple.


Other articles in the Assembled series:

Choosing the right CPU

How to choose your graphics card

All about motherboard basics

Selecting RAM, chassis case and Power Supply Unit

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