Raid Data Recovery Los Angeles
RAID Level 0
RAID Level 0 or striping is optimized for performance at the expense of
fault tolerance. Drives in a RAID 0 array organizes data in such a way
that it is striped across the multiple drives. A RAID Level 0 array can
contain any number of stripes. In RAID 0 if you have 2 x 60 gig drives
the array size will be 120 gig. The reason RAID 0 is a
performance-enhancing configuration is that striping enables the array
to access data from multiple drives at the same time. In other words,
since the data is spread out across a number of drives in the array, it
can be accessed faster because it's not bottled up on a single drive.
This is especially beneficial for retrieving very large files, since
they can be spread out effectively across multiple drives and accessed
as if it were the size of any of the fragments it is organized into on
the data stripes. The downside to RAID Level 0 configurations is that it
sacrifices fault tolerance, raising the risk of data loss because no
room is made available to store redundant data. If one of the drives in
the RAID 0 fails for any reason, there is no way of retrieving the lost
data as can be done in other RAID implementations described below.
RAID Level 1
The RAID Level 1 is achieved through disk mirroring, and is done to
ensure data reliability. RAID 1 also enhances read performance, but the
improved performance and fault tolerance are at the expense of available
capacity in the drives used. In RAID 1 if you have 2 x 60 gig drives the
array size will be 60 gig. In a RAID Level 1 configuration, the RAID
management software instructs the subsystem's controller to store data
redundantly across a number of the drives (mirrored set) in the array.
In other words, the same data is copied and stored on different disks
known as mirroring to ensure that, should a drive fail, the data is
available somewhere else within the array. In fact, all but one of the
drives in a mirrored set could fail and the data stored to the RAID 1
subsystem would remain intact. A RAID Level 1 configuration can consist
of multiple mirrored sets, whereby each mirrored set can be a different
capacity. Usually the drives making up a mirrored set are of the same
capacity. If drives within a mirrored set are of different capacities,
the capacity of a mirrored set within the RAID 1 subsystem is limited to
the capacity of the smallest-capacity drive in the set. The read
performance gain can be realized if the redundant data is distributed
evenly on all of the drives of a mirrored set within the subsystem. The
number of read requests and total wait state times both drop
significantly; inversely proportional to the number of hard drives in
the RAID.
RAID Level 2
RAID Level 2 is rarely used in commercial applications, but is another
means of ensuring data is protected in the event drives in the subsystem
incur problems or otherwise fail. This level builds fault tolerance
around Hamming error correction code (ECC), which is used as a means of
maintaining data integrity. ECC tabulates the numerical values of data
stored on specific blocks in the virtual drive using a special formula
that yields what is known as a checksum. The check-sum is then appended
to the end of the data block for verification of data integrity when
needed. As data gets read back from the drive, ECC tabulations are again
computed, and specific data block checksums are read and compared
against the most recent tabulations. If the numbers match, the data is
intact; if there is a discrepancy, the lost data can be recalculated
using the first or earlier checksum as a reference point.
RAID Level 3
This RAID level is really an adaptation of RAID Level 0 that sacrifices
some capacity, for the same number of drives, but achieves a high level
of data integrity or fault tolerance. It takes advantage of RAID Level
0's data striping methods, except that data is striped across all but
one of the drives in the array. This drive is used to store parity
information that is used to maintain data integrity across all drives in
the subsystem. The parity drive itself is divided up into stripes, and
each parity drive stripe is used to store parity information for the
corresponding data stripes dispersed throughout the array. This method
achieves very high data transfer performance by reading from or writing
to all of the drives in parallel or simultaneously but retains the means
to reconstruct data if a given drive fails, maintaining data integrity
for the system. RAID Level 3 is an excellent configuration for moving
very large sequential files in a timely manner. The stripes of parity
information stored on the dedicated drive are calculated using an
"Exclusive OR" function, which is a logical function between the two
series that carries most of the same attributes as the conventional OR
function. The difference occurs when the two bits in the function are
both non-zero: in Exclusive OR, the result of the function is zero,
wherein with conventional OR it would be one.
RAID Level 4
RAID Level 4 is similar in concept to RAID Level 3, but emphasizes
performance for different applications, e.g. Database TP versus large
sequential files. Another difference between the two is that RAID Level
4 has a larger stripe depth, usually of two blocks, which allows the
RAID management software to operate the disks much more independently
than RAID Level 3. This essentially replaces the high data throughput
capability of RAID Level 3 with faster data access in read-intensive
applications. A shortcoming of RAID level 4 is rooted in an inherent
bottleneck on the parity drive. As data gets written to the array, the
parity encoding scheme tends to be more tedious in write activities than
with other RAID topologies. This more or less relegates RAID Level 4 to
read-intensive applications with little need for similar write
performance. As a consequence, like its Level 3, it doesn't see much
common use in commercial applications.
RAID Level 5
This is the last of the most common RAID levels in use, and is probably
the most frequently implemented. RAID Level 5 minimizes the write
bottlenecks of RAID Level 4 by distributing parity stripes over a series
of hard drives. In doing so it provides relief to the concentration of
write activity on a single drive, which in turn enhances overall system
performance. The way RAID Level 5 reduces parity write bottlenecks is
relatively simple. Instead of allowing any one drive in the array to
assume the risk of a bottleneck, all of the drives in the array assume
write activity responsibilities. The distribution frees up the
concentration on a single drive, improving overall subsystem throughput.
RAID Level 5's parity encoding scheme is the same as Levels 3 and 4; it
maintains the system's ability to recover any lost data should a single
drive fail. This can happen as long as no parity stripe on an individual
drive stores the information of a data stripe on the same drive. In
other words, the parity information for any data stripe must always be
located on a drive other than the one on which the data resides.
Emergency data recovery from hard disk drives and other media is our specialty. We can recover data from:
The turn around time for Data Recovery is the fastest in the
industry, with as little as 1 hour to 24 hours for high end recovery
before your information is back in your hands.
For the latest information about
Data Recovery Los Angeles
Our hard disk data recovery engineers have a world class reputation for recovering your data where others fail. All our data recovery work is carried out in-house with total confidentiality; we never outsource our work. Upon receipt of your media, the diagnosis stage will begin. After diagnosis, you will be sent a report detailing the data that can be recovered, along with the cost of recovery.
No matter how bad your situation looks we can try to recover data. Situations are rarely hopeless
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Avidware Consulting Services
When a RAID system has crashed, do not try to dismount the RAID array, or when more than one drive has crashed, do not try to start a "Rebuild". Use our services for professional, RAID Data Recovery.
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