HP StorageWorks 1500 Modular Smart Array Installation Guide (355901-004, October 2006)

Installation Procedures - All Deployments
31HP StorageWorks 1500 Modular Smart Array Installation Guide
Striping methods
A storage array combines the capacity of several physical hard drives into one
virtual unit called an array. These arrays are then presented to the operating
system as a single disk device. The physical layout of an array can be one of two
configurations:
■ Vertical striping—Offers ultimate fault tolerance and performance, but at the
price of storage efficiency.
■ Horizontal striping—Allows for the creation of large arrays and efficient use
of storage capacity, but at the price of I/O performance and less fault
tolerance.
In a vertical configuration, an array uses hard drives from separate storage
enclosures and different SCSI buses. In a horizontal configuration, the array uses
multiple drives contained within the same storage enclosure.
RAID levels
In conjunction with the striping method, the assigned RAID level also determines
the fault-tolerance, I/O performance, and storage efficiency of the LUN.
See Table 3 on page 32 for a comparison list of the different RAID levels.
When selecting a RAID level for a LUN, consider the type of data that will be
stored on the array. For example:
■ For transitional data you may want to use RAID 0, which provides no fault
tolerance, but provides rapid storage and access of large amounts of data.
■ For critical data use a fault-tolerant RAID level, such as RAID 1, RAID 1+0,
RAID 5, or RAID 6. Choose the RAID level that offers the desired
combination of fault-tolerance, I/O performance, and storage efficiency.
Depending on the assigned RAID level, one or more drives within a LUN can fail
without bringing the drive sub-system down.