SECTION I: UNDERSTANDING RAID AND RAID LEVELS
If you’re thinking about running a RAID setup, read this section of the guide, as each RAID level has positives and negatives. The guide does not rely on RAID, as you can run a single-drive server; however we will be going with RAID 5. Use the RAID calculator to find your final array size. The proceeding information is via LSI’s comprehensive user guide:
RAID is an array, or group, of multiple independent physical drives that provide high performance and fault tolerance.A RAID drive group improves I/O (input/output) performance and reliability. The RAID drive group appears to the host computer as a single storage unit or as multiple virtual units. I/O is expedited because several drives can be accessed simultaneously.
RAID drive groups improve data storage reliability and fault tolerance compared to single-drive storage systems. Data loss resulting from a drive failure can be prevented by reconstructing missing data from the remaining drives. RAID has gained popularity because it improves I/O performance and increases storage subsystem reliability.
SUMMARY OF RAID LEVELS
RAID 0 provides disk striping across all drives in the RAID drive group. RAID 0 does not provide any data redundancy, but RAID 0 offers the best performance of any RAID level. RAID 0 breaks up data into smaller segments, and then stripes the data segments across each drive in the drive group. The size of each data segment is determined by the stripe size. RAID 0 offers high bandwidth.
In RAID 1, the RAID controller duplicates all data from one drive to a second drive in the drive group. RAID 1 supports an even number of drives from 2 through 32 in a single span. RAID 1 provides complete data redundancy, but at the cost of doubling the required data storage capacity.
RAID 5 includes disk striping at the block level and parity. Parity is the data’s property of being odd or even, and parity checking is used to detect errors in the data. In RAID 5, the parity information is written to all drives. RAID 5 is best suited for networks that perform a lot of small input/output (I/O) transactions simultaneously.
RAID 5 addresses the bottleneck issue for random I/O operations. Because each drive contains both data and parity, numerous writes can take place concurrently.
RAID 6 is similar to RAID 5 (disk striping and parity), except that instead of one parity block per stripe, there are two. With two independent parity blocks, RAID 6 can survive the loss of any two drives in a virtual drive without losing data. RAID 6 provides a high level of data protection through the use of a second parity block in each stripe. Use RAID 6 for data that requires a very high level of protection from loss.
In the case of a failure of one drive or two drives in a virtual drive, the RAID controller uses the parity blocks to re-create all of the missing information. If two drives in a RAID 6 virtual drive fail, two drive rebuilds are required, one for each drive. These rebuilds do not occur at the same time. The controller rebuilds one failed drive, and then the other failed drive.
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.
There are MANY more RAID levels, but these are primarily the conventional ones adequate for our server build.