I have had the luck to work on a number of data storage projects. I have designed, tested, and re-architected San and Nas deployments. (That is, Storage Area Networks and Network Attached Storage.) Raid is always a component of these.
At my current position, we have a Compellent San. The Compellent offers tiered virtual storage.
The way this works is that there are actual Raid devices at various levels (Raid1, Raid5, Raid10). The volumes or virtual hard drives are assigned a Raid level. These virtual volumes are then carved out of the physical Raid devices. You can tier the volume so that frequently accessed data and rarely accessed data are at different Raid levels.
This allows different blocks on a server’s volume to be at Raid5 or Raid10. Why would you want to do this? Well, Raid10 is fast but takes up twice as much raw disk space. Thus you put the speed sensitive storage blocks on Raid10 and the rest on Raid5, maximizing your disk investment.
The Compellents are very cool technology. It came out in 2004, and now the idea has spread to other vendors. Still, they were the first and are our preferred vendor.
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