This document is not a summary of storage best practices. Its purpose is to assist in the answering of the question, "What RAID type do I configure my VMFS LUN as?" which is often asked in regards to local storage.
Summary of the different RAID types
Mirror and striping
Stripe with Parity
The data is striped across all the disks in the set. Not true RAID because it is not redundant.
Exact copies of the data are kept across paired disks or disk sets.
A striped array whose segments are a mirror set. Not to be confused with 0+1
The data is striped across all the disks in the RAID set, along with the parity information needed to reconstruct the data in case of disk failure.
Good. All IO is spread and no parity overhead
Twice the read rate but writes occur twice
Combines speed efficiency of the RAID 0 (stripe set) with a fault tolerance of RAID 1 (mirror).
High read and medium write performance. A good balance of performance and availability.
Data you can afford to loose, such a pre-production, image/video editing.
Data requiring high availability, such as accounting or payroll.
Transactional type data such as database logs.
File and application servers. Typically everything that does not have a specific requirement.
Capacity of one disk in the set. 33% for a 3 disk set.
Other elements to consider are
Hot spare disks can often be configured to provide a space to rebuild a redundant disk without attendance.
Some types of SAN behave differently under the hood and you should reference the vendor documentation and best practices. For example the HP EVA works quite differently and some vendors have RAID 6.
For optimal performance make sure VMFS is the only partition on LUN and make sure the LUN maps to it's own set of physical disks if possible.
A summary of raid types with an animated representation of how the blocks are arranged in each type. http://www.acnc.com/04_01_05.html
A description of different RAID types. http://www.z-a-recovery.com/art-raid.htm
ESX Storage Virtualization Insights by Thorbjørn Donbæk, Senior Storage Developer, VMware. http://www.vmware-tsx.com/download.php?asset_id=40
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