What to Look for in a Hard Drive

When looking for a hard drive there are plethora of things to look for but most commonly you want speed and space. Hard drives have improved over time from capacity to speed as well as from large server array drives to small microdrives which can easily fit in your pocket. Having large number of drives out there makes one confuse that how to pick the drive that is inexpensive, useful and what to look for in a hard drive as well as serves the purpose.

What to Look for in a Hard Drive

What to look for in a hard drive

When you want a perfect drive you should clearly know what is that you are looking in a drive. Either it’s the speed? Capacity of the drive? performance in your computer or the aesthetics. To make a better decision you can explore three broad categories of hard drive to make the best decision.

Performance

Performance can be the most common driving factor for some people. No one likes working on a slow computer. Hard drive performance impacts largely on a computer performance and it has the following attributes:

1. Interface
2. Rotation Speed
3. Access Times
4. Buffer Sizes

Interfaces

Broadly there are two interfaces which are common for hard drives: Serial ATA (SATA) and IDE (or ATA). Before these a SCSI interface was used go to get high performance on desktops but it has become limited to only server storage.

IDE interfaces are most commonly used in personal computers. In IDE there are number of speeds like ATA/33 to ATA/133. The most common speed standard is ATA/100 which also supports previous versions. The number indicates the maximum bandwidth in megabytes per second that the interface can bear. That said, ATA/100 interface is capable to support 100 MB/sec. At this time no hard drive can reach to these sustained transfer rates.

For Multiple Devices

The IDE standard has a major drawback that it comes to handling multiple devices. Each IDE controller has 2 channels can support 2 devices. Therefore, it should maintain speed for the slowest device on the channel. That’s why you will commonly see two IDE channels: one for hard drives and one for optical drives. If we use a hard drive and optical drive on the same channel then the controller scaling back the performance to the optical drive speed which in returns decreases the performance of the hard drive.

Serial ATA

This is the new interface and has become popular and is the best replacement of IDE interface. This is the simple interface that uses one cable per drive and can give speed between 150 MB/s up to 300 Mb/s with it’s latest version.

The major factor that defines the performance of the drives is the rotational speed. The higher the drive rotates the more read/write speed it can generate in particular time. The most common issue in hard drives in the heat and noise because of the higher rotational speed. Heat directly impacts the performance of electronic components and when there’s not a proper ventilation it can cause serious damage. Similarly, noise can cause distractions for people sitting beside the computer. Majority of the home PCs has drives which run at 7200rpm. While the higher speed server driver can run at 10,000 rpm.

Access Times

Access time define the time length that the drive head takes moving the position from platter for the appropriate function. There are basically four access times used for hard drives like:

  • Read Seek
  • Write Seek
  • Track to Track
  • Full Stroke

All of these are rated in milliseconds. Read seek refers to the time that head take to move from one position to the other on the drive to read the data. Write seek is the time that drive takes to write data from empty space and beginning the data. Track to track defines the time that a drive takes to move the drive head to each sequential track on the drive. Full stroke is the time that drive head takes to move from outer to inner portion of the disk of the full length of the drive head’s motion. All of these gives higher performance if they have lower number.

The last factor is the performance of the drive which is the amount of buffer on the drive. It’s basically the amount of RAM on the drive which is used to store frequent data access from the drive. Since RAM is much faster compared to hard drive at transferring data then the drive head position and increases the speed of the drive. So if the more buffer is used on the drive, the more data can reside in the cache to decrease the amount of physical drive operation. The drives we use today have 8MB buffer or some drives have 16MB buffer.

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