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					RAID
Redundant Arrays of Independent Disks
What exactly is a RAID?
RAID is basically drives stacked
on top of each other like a cake
with layers that can share their
data together.
What does RAID do?
Now imagine that the cake are you hard
drives and that frosting is the data. As you
can see that the 2 layer cake has the same
data as each other. Now pretend that
something eats a layer of the cake (Virus.)

Now is it was a single layer cake all the
frosting would be gone but since there is
more than one layer the same frosting
remains.

So basically a RAID, with more hard drives
can use one of the hard drives to act as a
backup in case something happens though
you lose potential data
Why should I use RAID?
In some cases you shouldn’t.
Luckily there are different levels of raid that we can use. For everyone's
personal benefit.
 RAID level 0
 This level is not actually considered a type of raid, and is fairly
 common. Its not RAID because this level is not redundant in the
 slightest and only uses one driver. Therefore the computer has no
 protection from a wiped out hard drive. It Works by stripping the data
 and Spreading the data between the Drives.
                                                   Drive 1   Drive 2

                                         Block 1     1         2

                                         Block 2     3         4

                                         Block 3     5         6
Pros: Faster (doesn’t repeat all
data.)
No loss of data capacity
Cons: Not redundant.
Raid Level 1
Basically one drive mirrors the other, however this slows
down the writing time by a ½. Mirrors the data in-between
drives.




      Pros: Completely Redundant
      Cons: Writing speed ½                   Drive 1   Drive 2

      Takes time to change.
                                   Block 1      1           1
      Need at least 2 drivers
                                   Block 2      2           2
      Halves possible data.
                                   Block 3      3           3
Raid level 0+1
This Raid strips, then mirrors combining Raid 0 and Raid 1. So you have the quickness
of 0 with the redundancy of 1

 Pros: Redundant
 Better performance
 Cons: Expensive (4 Drives or more aren’t cheap.)
 Less effective data then if you didn’t combine hard drives


                                                 Drive 1 Drive 2 Drive 3 Drive 4

                                      Block 1        1        2        1         2


                                      Block 2        3        4        3         4


                                      Block 3        5        6        5         6
Raid level 1+0
Basically the same as RAID level 0 + 1 except that the data is mirrored
then stripped making the data a little more protected.
Pros: Redundant, Better performance
Cons: Expensive, less effective data.



                                 Drive 1    Drive 2   Drive 3    Drive 4


                     Block 1        1         1          2          2

                     Block 2        3         3          4          4

                     Block 3        5         5          6          6
Raid level 5
Works on binary, and using odd and even numbers, I’m not quite sure. But if one of
the drives is damaged it will actually repair itself.
Pros: Better array performance Redundent.
Can perform a hot swap. (Switch hard drives while computer is operating.
Cons: Need 3 drives
When it rebuilds your performance will degrade.




                                            Drive 1       Drive 2          Drive 3

                        Block 1               1              2               P

                        Block 2               3              P               4

                        Block 3               P              5               6
There was also Raid level 2, 3,
and 4 but they didn’t work out,
so they were never released.
        So you could say they failed…
  Not that badly however.




To sum it up, most people have RAID 1 or RAID 0, which is all they really need.
But for any small business and bigger you might need RAID 5, RAID 1+0, or
RAID 0+1 to protect your data.
   The history of RAID.
Or at least what I could find.
Patented 1987
Built in 1989
Updated several times



         That’s all I could find. Until I made these
         updates….
 The History of RAID revamped.

1956 – IBM officially announces the
RAMAC 305
1961 – Ampex develops helical scanning
video recording, which well later be adapted for
high-capacity tape backup.
1962 – IBM Advanced disk file used one head
for each disk surface, which eliminates the need
for compressed air to position heads.
1973 – IBM’s hermetically sealed Winchester
hard disks become the standard design for disk
drives.
1979 – Philips demonstrates optical storage drive
technology as part of a joint venture with control data
corp.
1988 – David A. Patterson leads a team that
defines RAID standards for improved performance,
reliability.
1995 – EMC develops the concept of network-
attached storage
1998 – Gigabit Ethernet becomes a formal IEEE
standard.


                           The end of my
                           revamped history
Some RAID release times.
       Raid 0 was released on
       march 5, 2004
       Raid 1 was released on
       June 5, 2007
       Raid 5 was released in
       1995, on June 8.
       Raid 1+0 was released
       on June 7, 2007
Who makes RAID?
IstarUSA StarTech
High Point Areca
SYBA       Accusys
Rosewill   Addonics
3ware
Adaptec
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=B
ESTMATCH&Description=raid

     http://www.computerworld.com/s/article/87093/The_Story_So_Far

              http://www.cuddletech.com/veritas/raidtheory/x62.html


        http://www.computerworld.com/s/article/87093/The_Story_So_Far

      http://www.staff.uni-mainz.de/neuffer/scsi/what_is_raid.html

   http://compreviews.about.com/od/storage/l/aaRAIDPage1.htm

    http://www.pcguide.com/ref/hdd/perf/raid/whyShould-c.html
THE
END

				
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posted:8/12/2011
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