Raid Implementation; Raid 5 Overview - IBM DS8800 Introduction And Planning Manual

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RAID implementation

RAID 5 overview

24
Introduction and Planning Guide
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Storage Manager.
The first management console in a storage complex is always internal to the 242x
machine type, Model 941 and Model 951. To provide continuous availability of
your access to the management console functions, use a second management
console, especially for storage environments using encryption. For more
information, see "Best practices for encrypting storage environments" on page 79.
This second management console can be provided in two ways:
v External (outside the 242x machine type, Model 941 and Model 951). This
console is installed in the customer-provided rack. It uses the same hardware as
the internal management console.
Note: The external HMC must be within 50 feet of the base model.
v Internal The internal management console from each of two separate storage
facilities can be connected in a "cross-coupled" manner. Plan for this
configuration to be accomplished during the initial installation of the two
storage facilities to avoid additional power cycling. (Combining two previously
installed storage facilities into the cross-coupled configuration at a later date,
requires a power cycle of the second storage facility.) Ensure that you maintain
the same machine code level for all storage facilities in the cross-coupled
configuration.
RAID implementation improves data storage reliability and performance.
Redundant array of independent disks (RAID) is a method of configuring multiple
disk drives in a storage subsystem for high availability and high performance. The
collection of two or more disk drives presents the image of a single disk drive to
the system. If a single device failure occurs, data can be read or regenerated from
the other disk drives in the array.
RAID implementation provides fault-tolerant data storage by storing the data in
different places on multiple disk drive modules (DDMs). By placing data on
multiple disks, I/O operations can overlap in a balanced way to improve the basic
reliability and performance of the attached storage devices.
Physical capacity can be configured as RAID 5, RAID 6 (only on the DS8000
series), RAID 10, or a combination of RAID 5 and RAID 10. RAID 5 can offer
excellent performance for most applications, while RAID 10 can offer better
performance for selected applications, in particular, high random, write content
applications in the open systems environment. RAID 6 increases data protection by
adding an extra layer of parity over the RAID 5 implementation.
You can reconfigure RAID 5 disk groups as RAID 10 disk groups or vice versa.
RAID 5 is a method of spreading volume data across multiple disk drives. The
DS8000 series supports RAID 5 arrays.