HP StorageWorks 4400, Installation Manual

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• Striping methods
• RAID levels
• Hard drive sizes and types
• Spare drives
• Array sizing (capacity)
NOTE:
For the minimum supported configuration, and other configuration information, see the QuickSpecs
document at:
http://www.hp.com/go/eva4400
System and performance expectations
To help determine the best way to configure your storage, rank the following three storage
characteristics in order of importance:
• Fault tolerance (high availability)
• I/O performance
• Storage efficiency
With your priorities established, you can determine which striping method and RAID level to use.
As highlighted in the following section, some configuration methods offer greater fault tolerance, while
other configuration methods offer better I/O performance or storage efficiency.
RAID levels
Vraid is the HP term for implementation of RAID ( R edundant A rray of I ndependent D isks) storage.
Vraid is also referred to as redundancy in HP management software. Virtual disks with HP Vraid use
three key RAID methods: data striping, data mirroring, and parity error checking. Unlike traditional
RAID, all HP Vraid levels distribute data across
all available physical disks.
Data striping improves speed by performing virtual disk I/O with an entire group of physical disks
at the same time. Mirroring provides data redundancy by storing data and a copy of the data. Parity
also provides data redundancy by storing data and the calculated parity for each stripe of data. If a
subset of the data on a physical disk becomes corrupt or the entire physical disk fails, the data can
be automatically recovered from redundancy so that data loss does not occur.
The EVA has four Vraid types: Vraid0, Vraid1, Vraid5, and Vraid6. Each Vraid type provides unique
I/O speed and has a different level of data redundancy, which directly effects the amount of physical
space used. Once a virtual disk is created, its Vraid type cannot be changed.
Review and confirm your plans 18