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