According to UniRecovery RAID Data Recovery Labs, External Hard Disk Drives provide great flexible storage option and security by providing a mobile back up option, yet this advantage has dangerous twist to users.
With storage capacity running in hundreds of Gigabites, accompanied by high rates of data transfer, in addition to the flexibility to plug the external drive to a Laptop, Desktop, Server, Memory Cards, Camera or iPod and sold at reasonable prices have increased their popularity dramatically.
However, as the popularity of the external drives containing backups and valuable data are increasingly failing for no apparent reasons. Majority of these failing drives are often of well known commercial brands such as Lacie, Freecom and Omega and with the latest high capacity Maxtor, Seagate or Western Digital hard disk drives models with storage capacity exceeding 320Gb or even 400Gb on a single drive.
According to a study of 100,000 drives conducted by Carnegie Mellon University, it is widely believed Hard Disk Drive vendors manipulate the (MTTF) - mean time to failure. In fact The mean time to failure (MTTF) of drives, according to their manufacturers, vary from 1,000,000 to 1,500,000 hours, suggesting a nominal annual failure rate of at most 0.88%. Whereas the study finds that “up to 13% observed on some systems. ". This suggests that field replacement is a fairly different process than one might predict based on datasheet MTTF.
It has also been established that failure rate is not constant with age, and that, rather than a significant infant mortality effect, evidently a significant early onset of wear-out degradation. That is, replacement rates in research data grew constantly with age, an effect often assumed not to set in until after a nominal lifetime of 5 years. The study, also carefully point out that the study didn't necessarily track actual drive failures, but cases in which a customer decided a drive had failed and needed replacement. The study also explains that no vendor-specific failure information, and that his goal is not “choosing the best and the worst vendors" but to help them to improve drive design and testing. Also, little difference in replacement rates between SCSI, FC and SATA drives, potentially an indication that disk-independent factors, such as operating conditions, affect replacement rates more than component specific factors. On the other hand, we see only one instance of a customer rejecting an entire population of disks as a bad batch, in this case because of media error rates, and this instance involved SATA hard disks
Time between replacements, a proxy for time between failure, is not well modelled by an exponential distribution and exhibits significant levels of correlation, including autocorrelation and long-range dependence.
Generally, inside the slick casings, often are poorly ventilated or even not ventilated at all, external hard drives assemblers include the cheapest available drives such as Maxtor & Seagate, combined with badly ventilated enclosure casing, the combination is catastrophic for any given user, especially when the hard disk drive is of high capacity containing crucial back-up data For any given Lacie with multiple drives, this can be a terrible experience with RAID drives and data in excess of 1 terabite. Often with RAID array external drives, the drive failure are more frequent and the damage is more extensive than single drives. According to Haj Majed Aziz of UniRecovery – RAID Data Recovery Labs “many of the 1 terabyte LaCie external drives contain 250Gb Maxtor IDE in RAID array, inside badly ventilated enclosures, when used on regular basis, especially within office environment, they are utter disaster. ”
Hitachi has unveiled a drive which has reached the new heights of one terabyte (TB). Its drive looks like any other, but uses perpendicular magnetic recording to make space for all that data. The current technology generation of LRT-Longitudinal Recording Technology, which records the bits laying horizontally, has been superseded by the recording of the bits standing vertically. However the cost is in the region of $18,000 !
UniRecovery- http://www.unirecovery.co.uk/apple-mac.php Apple MAC data recovery Laboratory