Special Report

The evolution of RAID data protection

Industry experts say the shape of RAID has evolved in the last 20 years, but the core concept of combining drives for data protection lives on regardless of the methods used.

Table of contents
 RAID changes its stripes, but not its value
 Post-RAID products
 Determining the number of drives in a RAID group

 RAID changes its stripes, but not its value

Experts say storage systems conceived during the last five years or so from Compellent Technologies Inc., EqualLogic Inc. (now part of Dell Inc.), LeftHand Networks Inc. (now part of Hewlett-Packard Co.) and 3PAR use alternatives to traditional RAID, such as distributed parity schemes and wide striping.

EMC Corp.'s Atmos and IBM Corp.'s XIV Storage System are new versions of storage systems that use distributed parity. Other systems that hit the market in 2008, such as Atrato Inc.'s Velocity 1000 (V1000) and Xiotech Corp.'s Emprise platform, use new technologies to avoid RAID rebuilds. However, there's disagreement in the industry over whether those systems are RAID or not.

→ Editor's Tip: Read this article to learn more about the new approaches to RAID.


 Post-RAID products

With more capacity on disk and more disks being crammed into arrays, it raises the potential not only for disk failures, but multiple disk failures. Without more advanced RAID algorithms to pick up that slack or a new approach to redundancy, data will be lost.


In response, vendors are starting to take new approaches to providing redundancy and data protection in disk arrays that don't use traditional parity RAID and rebuild approaches.

→ Editor's Tip: Read this article to get a chronological list of the post-RAID products introduced this year.

 Determining the number of drives in a RAID group

You know you need storage, and you have a pretty good idea of how to size the SAN layer. But how do you go about determining the correct number and proper type of disks? How many drives in a RAID group will it take to give you the performance you need for a database or email or file server, or for that new VMware implementation? Can you have too many drives in a RAID group, or even in the actual storage RAID array? We cover these parameters for the RAID array and underlying disk technology. When should you use SAS, SATA, FC or SCSI? What are the other metrics for sizing storage arrays, such as optimal max spindles per controller? What about the other vendor performance specifications?

→ Editor's Tip: Read this article to learn more about comparing and selecting RAID types.


This was first published in January 2009

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