RAID Disc System
Novell narrowed the definition of the concept of mirroring and duplication added
(duplexing). According to Novell terminology, mirroring refers to the pair of
discs when they are connected to the server or PC via an HBA, while duplication
implies that mirror pairs of disks connected via separate HBA. Duplication
provides redundancy entire disk channel, including HBA, cables and disks, and
allows multiple productivity.
RAID-3 requires a minimum of three identical disks. Often this technology is
called "n minus 1; (n-1) as the maximum capacity of the system is defined as all
disks in the array number (n) minus one disk for parity. RAID-3 uses the writing
method, called stratification of bits (bit interleaving), the data are written
to all disks pobitovo. For each recorded at the byte on the disk n- ; disk
parity "is written parity bit. This is a very slow process, because before
information about parity can be generated and stored at ; parity disk, the data
must be recorded for each of n- disc array. You can enhance the performance of
RAID-3 through synchronization mechanisms speed drives, so that they work
strictly ; in the leg. " However, due to restrictions on the use of performance
RAID-3 has fallen sharply, and today is sold very few products for servers based
on RAID-3. RAID-5 is the most popular market network servers RAID implementation.
Like RAID-3, it requires a minimum of three identical disks. However, unlike
RAID-3, RAID-5 produces alternating blocks of data without the use of the
selected drive for parity. And data, and a checklist amount recorded across the
array. This method allows for independent reading and writing to disk, and also
allows the operating system or RAID controller to hold several parallel
operations, I / O.
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