Tuesday, 26 May 2015 00:00

Knowledge in the nutshell about RAID 1

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Mirrored volume of the first level, creates copies of data on two or more disks. Most solutions, however, limits the number to two. You can work around this limitation by creating a nested array (eg RAID 1 with two RAID 1, which means RAID 11) of more in the description of RAID 10. In theory, the matrix of the first level provides the multiplication of performance in read similar to RAID 0, by reading the data from all components disks at a time.

In practice, neither Windows 7, either built into the SB950 RAID, are not allowed, and the Adaptec allow for it only when read caching enabled. The recording should be unchanged, or be equal like for a single disk. Capacity of RAID 1 is the smallest size of the carrier component, which can be regarded as the biggest disadvantage. The advantage is almost geometric increase in reliability with each disk in the array, and a very simple implementation. Data is stored in a practically unchanged and a single disk with such a matrix can work independently.

Geometric increase reliability RAID 1, you can specify the approximate formula rn, where r means the reliability of a single disk, and n is the number of disks in the array. How easy it count if, for example, our drives have a 5% chance of damage, it's mean that the matrix RAID 1 (composed of two disks) under ideal and statistical independent conditions would be 0.25%. But in reality is not as colorful. Most arrays use a twin models of drive, bought, and probably produced in the same time. In addition, hard work in similar conditions, which implies that the chances of damage them in similar time to grow. The ultimate reliability of RAID 1 is reduced to the chance to damage the last smooth disk in the array at time which will take to detect failures, replacement of the disk (s) and the reconstruction of matrix.

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We mentioned at first, that should not be confused the backups with RAID. Arrays with redundancy, practically all of the levels marked number from one upwards, protect us from losing data in case of damage to the physical disks. However, we do not protect against data corruption, eg by a virus, accidental overwriting / deletion / change, or even just simple of writing errors. If we want to fully protect our data, RAID give us continuous access to them, because the even breakdown will not block our access, but for the full confidence, made backed security is still necessary.

One of the advantages of RAID 1 is ease of implementation. This allows not only easy way to mirror / multiply the number of drives but also controllers. There is nothing on the way to building a RAID 1 in Windows 7, use a two disks connected to two independent controllers such as the built-in chipset and additional. This procedure is called fission or duplexing (if the matrix has two disks) or multiplexing (in the case of multiple drives). This solution protect us from writing hardware errors. If one of the controllers writes data with errors that we still have the second drive plugged into another efficient controller. Unfortunately, viruses and user errors remain a problem. Easy to implement also gives the advantages of the administration of RAID 1. Since in most cases, damage (only working on one disk) array will retain the full performance of one disk, there is nothing in the way of remove a drive to implement backup. Or you can simply hide the drive and in its place to connect a new one. Of course, depending on how it we will do, the synchronization may be needed (the reconstruction matrix).

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In the first paragraph we told that, in theory, RAID 1 thanks to an independent capability to read data from multiple disks, similar to RAID 0, should multiply the read performance. In addition, the access time to data on two drives should fall by half, and this, as opposed to RAID 0, regardless of the characteristics of that access, so thanks to that, that a full copy of the data is present on everydisk constituent. In practice, many implementations of RAID 1 is able to read the data at once with only one disk, and if even read from both, so the associated overhead with moving the head to the next sector, except for those already read on the remaining disks can effectively offset any gains in the case of sequential transfer. Correct in the records does not exist, because all data must be at the same time saved on hard disks, and lack of complex calculations in this connection does not slow down. Finally, RAID 1 will have a performance similar to a single drive and will give us only the protection against drive failure for the price of capacity of one disk (in the case of matrix of two disks).

Last modified on Tuesday, 26 May 2015 19:43
Data Recovery Expert

Viktor S., Ph.D. (Electrical/Computer Engineering), was hired by DataRecoup, the international data recovery corporation, in 2012. Promoted to Engineering Senior Manager in 2010 and then to his current position, as C.I.O. of DataRecoup, in 2014. Responsible for the management of critical, high-priority RAID data recovery cases and the application of his expert, comprehensive knowledge in database data retrieval. He is also responsible for planning and implementing SEO/SEM and other internet-based marketing strategies. Currently, Viktor S., Ph.D., is focusing on the further development and expansion of DataRecoup’s major internet marketing campaign for their already successful proprietary software application “Data Recovery for Windows” (an application which he developed).

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