IBM ServeRAID, User Reference

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A sub-logical drive is created
within
each array (A, B, and
C). Then, the data is striped
across the physical drives in
the array, creating blocks.
Notice that, in each array, the
data on the drive on the right
is a copy of the data on the
drive on the left. This is
because the sub-logical drives
(A, B, and C) are RAID
level-1 in a RAID level-10
implementation (see the
following table).
A A
B C
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
A
*
Then, create a logical drive
within the spanned array (*).
The data is striped across this
logical drive, creating blocks
(1-12). Notice that none of
these blocks are redundant.
This is because the logical
drive is RAID level-0 in a
RAID level-x0 implementation
(see the following table).
A A
B C
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
1
2
3
4
5
7
6
8
A
1
*
2 3
5 4
7
10
8
11
6
9
12
RAID level Sub-logical drive Spanned array logical drive
00 RAID level-0 RAID level-0
10 RAID level-1 RAID level-0
1E0 RAID level-1E RAID level-0
50 RAID level-5 RAID level-0
With RAID level-10, level-1E0, and level-50, if one of the physical drives fails in a
sub-logical drive, the ServeRAID controller switches read and write requests to the
remaining functional drives in the sub-logical drive. With RAID level-00, a physical
drive failure within the sub-logical drive results in loss of data.
RAID level-x0 offers the following advantages and disadvantages.
Advantages Disadvantages
v Supports up to 60 physical drives
v 100% data redundancy (except for RAID
level-00)
v Available only on the ServeRAID-4 and
ServeRAID-5i controllers
v
No data redundancy for RAID level-00
Chapter 3. Understanding RAID technology
31