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    Arrow RAID Levels RAID 0 RAID 1 RAID 5 ...

    RAID stands for Redundant Array of Independent Disks and it basically involves combining two or more drives together to improve the performance and the fault tolerance. Combining two or more drives together also offers improved reliability and larger data volume sizes. A RAID distributes the data across several disks and the operating system considers this array as a single disk.

    RAID Levels
    Several different arrangements are possible and different standard schemes have evolved which represent a set of trade-offs between capacity, speed and protection against the data loss.

    Some of the common RAID levels are -
    RAID 0
    RAID 0 uses data stripping as the data is broken into fragments while writing it to the drive. The fragments are then written to their disks simultaneously on the same sector. While reading, the data is read off the drive in parallel and so, this type of arrangement offers huge bandwidth.

    The trade-off associated with RAID 0 is that a single disk failure destroys the entire array as it offers no fault tolerance and RAID 0 does not implement error checking.

    RAID 1
    RAID 1 uses mirroring to write the data to the drives. It also offers fault tolerance from the disk errors and the array continues to operate efficiently as long as at least one drive is functioning properly.

    The trade-off associated with the RAID 1 level is the cost required to purchase the additional disks to store data.

    RAID 2
    It uses Hamming Codes for error correction. In RAID 2, the disks are synchronized and they're striped in very small stripes. It requires multiple parity disks.

    RAID 3
    This level uses a dedicated parity disk instead of rotated parity stripes and offers improved performance and fault tolerance. The benefit of the dedicated parity disk is that the operation continues without parity if the parity drive stops working during the operation.

    RAID 4
    It is similar to RAID 3 but it does block-level stripping instead of the byte-level stripping and as a result, a single file can be stored in blocks. RAID 4 allows multiple I/O requests in parallel but the data transfer speed will be less. Block level parity is used to perform the error detection.

    RAID 5
    RAID 5 uses block-level stripping with distributed parity and it requires all drives but one to be present to operate correctly. The reads are calculated from the distributed parity upon the drive failure and the entire array is not destroyed by a single drive failure. However, the array will lose some data in the event of the second drive failure.

    The above standard RAID levels can be combined together in different ways to create Nested RAID Levels which offer improved performance. Some of the known Nested RAID Levels are -

    RAID 0+1
    RAID 1+0
    RAID 3+0
    RAID 0+3
    RAID 10+0
    RAID 5+0
    RAID 6+0


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  6. #2
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    شكرا محمد كتير ليك
    Eng Ahmed El-Desoki
    Network and System Engineer
    FCI Graduated
    CCNA + MCSE (Security + Messaging)

    لو بطلت احلم اموت
    لو عاندت اقدر افوت


    شرف عظيم و رفيع المستوى لاى مصرى ان يكون خريج او طالب بكلية الحاسبات والمعلومات

    يرخص الغالى ليك يا حبيبى يا مالك حالى انت يا حبيبى
    يا كلية الحاسبات و المعلومات

    FCI = Faculty of Computers and Informatics



    الحمد لله رب العالمين الذى اكرمنى بنعمة الحج . اللهم يارب لا تخرجنى من السعودية ابدا لكى استطيع كل عام ان احج الى بيتك الحرام
    اللهم يارب لن استحى ان ادعوك كل عام ان احج الى بيتك العظيم فلو قطعت رزقى من الحج فاقطع رزقى من الحياة قبل ان تاتى هذة اللحظة
    اللهم يارب اكرم كل المسلمين و المسلمات بحج بيتك الحرام . يارب انك سميع قريب تجيب دعوة الداعى اذا دعاك . الحمد لله رب العالمين


    من مواضيع ahmed_desoki :


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  10. #5

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    بسم الله الرحمن الرحيم
    ألف شكر يا أستاذ محمد على المعلومات ، وفقكَ الله لكل خير ، اللهم ءامين

    :d

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