Several Arrays On One Hard Drive
This feature has been rare until now: A hard drive does not have to be incorporated into an array in full, but rather can function in two or three arrays for some sectors.
What good is that, you ask? If you wanted to expand a RAID 5 array consisting of four hard drives, each with 200 GB, to two more drives, you could, in the future, also use two 300 GB hard drives. Because 100 GB on each hard drive would go unused, Fulcrum allows an additional array to be generated spanning these two. A RAID 0 for temporary data, perhaps?
This feature could be important in the low-cost market - just think of configurations with only two hard drives: The first half of the two drives could be used as RAID 0 - perfect for the operating system including the storage file. On the second section of the drives, we mirror the data in a RAID 1. If one of the hard drives fails, a replacement drive would have to be procured and Windows re-installed. Your really important data, however, is mirrored on both hard drives and is instantly available!
Another scenario would be the simultaneous use of several hard drives for two applications. For example, if there were 8 drives with 100 GB each. In RAID 5, 700 GB would be available (the capacity of a drive would not apply to parity data). If we make do with only 500 GB, there would still be enough room to install a 200 GB RAID 0 spanning the same drives. This would produce a "secure" data sector with RAID 5 and a very fast sector for temporary data. What more could be desired ...
We tried this scenario with both the RAIDCore adapter and Adaptec's 2200S. It only worked without errors with RAIDCore.
We put two arrays onto all eight hard drives simultaneously: The first array is a RAID 0, the second a RAID 5 with a distributed spare. The result is a fast 20 GB drive and a drive with more than 200 GB for medium-term storage of important data.
