Avago Technologies MegaRAID Fast Path Software - Manual (Page 37)

LSI Corporation Confidential | July 2011 Page 37
MegaRAID SAS Software User Guide Chapter 2: Introduction to RAID | RAID Levels
By breaking up a large file into smaller segments, the RAID controller can use both SAS
drives and SATA drives to read or write the file faster. RAID 00 involves no parity
calculations to complicate the write operation. This situation makes RAID 00 ideal for
applications that require high bandwidth but do not require fault tolerance.
Table 11
provides an overview of RAID 00. Figure 11 provides a graphic example of a RAID 00
drive group.
Figure 11: RAID 00 Drive Group Example with Two Drives
2.5.8 RAID 10 RAID 10 is a combination of RAID 0 and RAID 1, and it consists of stripes across mirrored
drives. RAID 10 breaks up data into smaller blocks and then mirrors the blocks of data
to each RAID 1 drive group. The first RAID 1 drive in each drive group then duplicates its
data to the second drive. The size of each block is determined by the stripe size
parameter, which is set during the creation of the RAID set. The RAID 1 virtual drives
must have the same stripe size.
Spanning is used because one virtual drive is defined across more than one drive
group. Virtual drives defined across multiple RAID 1 level drive groups are referred to as
RAID level 10, (1+0). Data is striped across drive groups to increase performance by
enabling access to multiple drive groups simultaneously.
Each spanned RAID 10 virtual drive can tolerate multiple drive failures, as long as each
failure is in a separate drive group. If drive failures occur, less than total drive capacity is
available.
Configure RAID 10 by spanning two contiguous RAID 1 virtual drives, up to the
maximum number of supported devices for the controller. RAID 10 supports a
maximum of 8 spans, with a maximum of 32 drives per span. You must use an even
number of drives in each RAID 10 virtual drive in the span.
Table 11: RAID 00 Overview
Uses Provides high data throughput, especially for large files. Any environment
that does not require fault tolerance.
Strong points Provides increased data throughput for large files.
No capacity loss penalty for parity.
Weak points Does not provide fault tolerance or high bandwidth.
All data lost if any drive fails.
Drives 2 through 256
Segment 1 Segment 2 Segment 3 Segment 6 Segment 8 Segment 5 Segment 7
Segment 9 Segment 11 Segment 13 Segment 15 Segment 10 Segment 12 Segment 14 Segment 16
Segment 4
... ... ... ...
RAID 0 RAID 0 RAID 0 RAID 0
RAID 00
RAID 0
Segment 17 Segment 18 Segment 19 Segment 20 Segment 21 Segment 22 Segment 23 Segment 24