|RAID level||# drives||500GB SATA||1TB SATA|
In the first two rows, the numbers appear as expected. For example, 96 drives would be 12 sets of 6+2 RAID ranks, meaning 72 drives' worth of data, so nearly 36TB for 500GB drives, and nearly 72TB for 1TB drives. With 14+2 RAID-6, thenyou would have 84 drives' worth of data, so 42TB and 84TB respectively match expectations.
Where EMC appears miscalculating is having 20x more drives, as the numbers don't match up. For 1920 drives inRAID-6, you would expect 20x more usable capacity than the 96 drive configurations. For 6+2 configurations, one would expect 720TB and 1440TB respectively. For 14+2 configurations, one wouldexpect 840TB and 1680TB, respectively.
Perhaps EMC DMX-4 can't address more than 600TB for the entire system? Does EMC purposely limit the benefitsof these larger drives? It does question why someone might go from 500GB to 1TB drives, if the maximum configuration only gives about 40TB more capacity.Fellow IBM blogger Barry Whyte questioned the use of SATA in an expensive DMX-4 system, in his post[One Box Fits All - Or Does It], and now perhaps there are good reasons to question 1TB from a capacityperspective as well.