Which Hard Drive?

The humble hard drive has really evolved over the years. It has been growing in capacity and spindle speed, reducing the power consumed, and has improved MTBF (mean time between failure) and reliability. Today, you can't just take a desktop drive and place it in a storage array or a server, just because it has the required spindle speed and capacity.You have to first understand the difference amongst different types of hard drives before zeroing in on the right one.

Which Desktop HDD?

Storage capacity of desktop HDDs has reached the 3 TB mark, but obviously such high capacity would only be useful for special functions, such as graphics designers and multimedia professionals. For ordinary users in an organization, typical hard drive capacity that's available these days is 100 GB. For power users, things to consider are hard drives with SATA 3.0 interface to get transfer rates up to 6 Gb/s, and higher cache buffer memory of 32 MB. Typical spindle speed in desktop drives is 7200 rpm.

There's another category called green drives available for desktops from all HDD manufacturers. They consume lesser power by varying their spindle speed between 5400 and 7200 rpm. They typically consume 6-8W during read/write operations, which is 3-5W lower than traditional HDDs.

Which enterprise HDD?

“Enterprise” hard drives are different from desktop drives as they're designed for higher reliability, performance and 24x7 operation, as required in servers and storage arrays. These drives have special firmware optimized for RAID usage. Since, RAID stresses the member hard drives and demands high availability; these drives also offer higher mean time between failures of above 1.2 million hours, which means 137 years of operation before drive failure. Unlike their desktop counterparts, these drives offer higher spindle speeds of 10,000-15,000 RPM and are also available with a Serial Attached SCSI (SAS) interface.

The capacity of enterprise hard drives is typically lower than the desktop drives. The highest capacity in enterprise drives can go up to 1 TB, while desktop drives have already touched 3 TB, as stated earlier.

SAS based enterprise drives are meant for servers running mission critical business applications, or transaction intensive applications. SATA based drives are typically used for building high-capacity storage solutions.

SSD vs. HDD

This is a long drawn debate that Solid State Drives (SSD) will replace the HDDs, but that would still take some years. The benefits of higher data transfer speeds of SSDs are negated by the high cost that they are currently available at. Also they do not offer such huge storage capacity as provided by traditional HDDs. Because of their light weight and speedier data transfer rates these drives should suit high-end notebooks, but also offer good use for enterprises.

For applications like accounting software or ERPs that require very high I/Os but not much storage requirement, adopting SSD is ideal in those cases. Such applications would not require much drive capacity and therefore even a 64 GB or a 128 GB SSD can provide sufficient space for OS, applications and their data files and in turn will churn out higher performance when compared to other enterprise class hard drives. To achieve such performance gains in enterprise applications, the price per GB should not be a limiting factor

Should you worry about the 4k standard?

Since the beginning of this year, all hard drive manufacturers have dumped the ancient 512 byte disk sector for a 4096 byte, ie 4k sector, also known as Advanced Format. So, what's in it that you should watch out for? This standard is not new and many HDD manufacturers have been shipping 4k sector drives for last two years or so. However, with this transition, lies a problem. Most computing systems assume that the sector size would be of 512 bytes and would keep requesting and receive data from a drive in 512 byte-size only. Also operating systems like Windows XP are not 4k aware.

Therefore misalignment can happen and that can de-grade the drive performance. So, if you are moving to a 4k supporting drive then users on Windows XP and those who use disk cloning software should be concerned. Windows versions after XP, ie Vista and Windows 7 already support this advanced format, and so their users should not face any difficulty while upgrading to these new drives. Even Mac users should have no concerns.

Windows XP does not align data automatically on 4k sector boundaries, and users will have to run a 3rd party utlity that aligns data from 512-byte sectors to 4k sectors so that HDD does not encounter errors while reading or writing data. Likewise if you clone Windows XP, Vista or Windows 7 from a 512-byte sector drive to the new 4k sector supporting drive, you'll need to run such aligning utility. Western Digital provides Advanced Format Align utility for their drives, while Seagate's new drives supporting Advanced Format have in-built alignment management firmware that eliminates the use of third party alignment utility software.