R.A.I.D consists
of a series of systems to
organize several disk drives into a single entity
that behaves as a single virtual drive but making
the various disks work in parallel ,therefore
improving the access performance and saving
the information stored from accidental crashes.
Disk Doctor Labs, Inc. Specializes in Raid
Recoveries, whether Stripe Sets with parity,
Volume Sets or Mirror Sets. Give us a call for
more information.
Recovery Process:
The Recovery process begins with a free
evaluation, where every drive in the raid array is
very carefully tested and the ones which are in
working condition will be cloned to our shop
media. The drives which are gone bad will go
under a more thorough diagnostic process, we
will than determine whether the defected drive
has a physical or logical problem, if diagnosed as
a physical problem it goes to our hardware
testing unit, and if some logical problem is
detected, then it will be handled by our software
unit. In some cases a defective drive has to go
through both units. The main priority is to make
the defective drive to be working again so we get
a cleaner bit by bit copy of the data. This process
may have to be repeated several time to get the
desired result. Once this process is complete, the
software and hardware groups work together to
fix any logical and/or hardware problems and to
work on reconstructing the raid system.
Reconstruction of the raid process may be
repeated several time to get all the desired
results.
The Initial FREE Evaluation takes approximately
between 6 - 24 hrs for our Lab technicians to
properly diagnose. (All depending on how many
drives contained in the RAID Array).
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Kinds of RAIDs:
RAID 0 (Stripping mode):
In this mode, all the disk devices are organized
alternatively so that blocks are taken equally
from all disks alternatively, in order to reach
higher efficiency. Since the probability of finding
a block of a file is identical for all disks, there are
force to work simultaneously thus making the
performance of the meta disk almost N times that
of a single disk.
RAID 1:
In this mode, the goal is to reach the highest
security of the data. Blocks of data are duplicated
in all physical disks (each block of the virtual disk
has a duplicate in each of the physical disks).
This configuration provides N times the reading
performance of a single device, but it degrades
writing operations. Read operations can be
organized to read N blocks simultaneously, one
from each device at a time. Similarly when writing
1 block it has to be duplicated N times, one for
each physical device. There is no advantage in
this configuration regarding storage capacity.
RAID 4:
In this mode the ultimate goal is to balance the
advantages of the type RAID0 and RAID1. Data is
organized mixing both methods. The physical 1
to N-1 are organized in striping mode (RAID0)
and the Nth stores the parity of the individual bits
corresponding to blocks 1 to N-1. If any of the
disks fails, it is possible to recover by using the
parity information on the Nth hard disk.
Efficiency during read operations is N-1 and
during write operations is 1/2 (because writing a
data block now involves writing also to the parity
disk). In order to restore a broken hard disk, one
only has to re-read the information and re-write it
(it reads from the parity disk but it writes to the
newly install hard disk).
RAID 5:
This type is similar to RAID4, except that now the
information of the parity disk is spread over all
the hard disks (no parity disk exists). It allows to
reduce the work load of the parity disk, that in
RAID4 it had to be accessed for every write
operation (now the disk where parity information
for a track is stored differs for every track). |
