When was raid 6 developed

Even though it was a RAID 6, when the second drive failed, it also caused the array to fail. After the replacement drives were installed, the system failed to rebuild, which meant the business critical data was not accessible.

The engineers at Ontrack virtually rebuilt the RAID 6 array with the two missing disks in order to recover the missing data. Due to the manufacturer-unique algorithm in a RAID 6 array, a rebuild of the secondary parity stripe from this specific system had not been completed before.

The Solution Due to the rebuild failure, missing data from two failed drives had not been replicated onto the new drives when the new drives were added. The Resolution The Ontrack developers quickly created the tools needed to improve the success of the recovery. Academic Editor: Laurence T. Received 23 Sep Revised 26 Dec Accepted 10 Jan Published 23 Feb Abstract Existing RAID-6 code extensions assume that failures are independent and instantaneous, overlooking the underlying mechanism of multifailure occurrences.

Introduction In modern data centers, RAID-6 credited for performance and reliability are among the most popular configurations to be deployed. Backgrounds and Motivation In this section, we describe the different failure modes and recovery methods in RAID systems and introduce the concept of multifailure degradation in reconstruction window.

Failure Modes Many researches on the massive disks have all shown that mainstream disk drives have device failures or whole-disk failure and sector failures [ 22 ]. Multifailure Degradation In fact, multiple failures happening at almost exactly the same time is hardly witnessed in real-world systems, which are quite different cases from ideal models for simplification of research. Figure 1. Coding methods Element example Involved element Merit Shortcoming Mirroring of single disk 1 Simple and can maximize reduction of reconstruction window for specific drive Only covering replicated drive, not able to cover other drives, causing imbalance and fluctuation Short combination 2 In between Full combination 5 Maximizing fault-tolerance for the whole system Unable to reduce reconstruction window.

Table 1. Feature comparison of three coding ways for X drive. Figure 2. The optimal reconstruction sequence of single failure in RDP. Figure 3. Figure 4. Rebuilding single failure with elements. Figure 5. Figure 6. The coding for parity elements in drive.

Figure 7. The general construction of parity as the XOR sum of parity with its corresponding element in drive. Figure 8. Table 2. Recover a 0 with parity of different length in Figure 8. Figure 9. Figure References A. Ma, R. Traylor, F. Douglis et al. Blaum, J. Brady, J. Bruck, and J. View at: Google Scholar J. View at: Google Scholar M. Blaum, T. Cortes, and H. View at: Google Scholar C. Huang and L. Goel and P. Wang, G. Li, and X. View at: Google Scholar Y. Wang and G.

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Bez, E. Camerlenghi, A. Modelli, and A. Elerath and J. Transactions on Computers , vol. Huang, M. Chen, and J. Plank, W. Pierce, and C. Fu, J. Shu, and X. Hu, G. Liu, and J. Rongdong, L. Guangming, and J. Huang, H. Simitci, Y. Xu et al. View at: Google Scholar. Once the data has finished rebuilding you can then remove the failed drive and replace it with a new one, which becomes the new hot spare.

It allows for data to be recreated even if two disks fail within the array. The dual-parity is spread across all the disks and takes the space of two drives. If a disk fails in a RAID 1 or RAID 5 the user should not exchange it with a new one before being sure that all data from the remaining drives are backed up.

In many cases, if the RAID system used disks that came out of the production line at the same time, the possibility that another drive will also fail soon is quite large. This is just one of the inherent dangers of RAID systems. Even with all the performance and data security benefits RAID offers, what many users especially home consumers forget and what everybody should keep in mind is that having a RAID system is not the same as having a backup.

RAID can be used in combination with backups and thus making the whole storage system much more secure, but a RAID is never to be used instead of a backup.

On the contrary, when a RAID system fails — for example because of a malfunctioning hardware RAID controller or more drives failing than the selected RAID level is geared for -, it is much more complicated to both get the RAID up and running again as well as to recover any lost data when hit by such an incident. NAS systems have become more and more affordable to home users, they use the build-in RAID levels in combination with other advanced storage technologies like deduplication to get as much space as possible out of their system.

This comes at a price: in many cases these systems are wrongly set up and when a failure arises, then the whole system breaks down. In these cases, data recovery experts like Ontrack attempt to reconstruct several data layers from the many technologies the user has implemented until the original data can be recovered.

Remember: negligence in the beginning can result in serious problems, high costs and possible data loss later! With this advice in mind, there is a huge possibility that RAID will have many more years of life left in it.

Even with many other, intuitive methods of storing data coming to market, it will most likely take a long time for RAID systems to vanish from the modern world of IT.