RAID And You (A Guide To RAID-0/1/5/6/xx)

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4c. RAID-0 Performance Scaling With # of Drives
One of the things I have always hated seeing here is people who have RAID-0 arrays with 7 or 8 drives. Aside from the clear danger of disk failure, RAID-0 may scale well with a few drives, but much less so as you add more. For example, versus one disk and assuming theoretical maximums:

1 Disk = Baseline
2 Disks = 1/2 Time Decrease = 50% performance increase vs. 1 disk
3 Disks = 2/3 Time Decrease = 16% performance increase vs. 2 disks
4 Disks = 3/4 Time Decrease = 9% performance increase vs. 3 disks
5 Disks = 4/5 Time Decrease = 5% performance increase vs. 4 disks
6 Disks = 5/6 Time Decrease = 3% performance increase vs. 5 disks

And one must take into account the fact that as the number of drives increase, so too does the minimum size of the file required to be considered a "large" file. Add in the fact that overhead alone accounts for a few % of performance and you can see that past 3 disks your *theoretical maximum* increase is sitting in the low to mid single digit range.

This is so not true. Raid 0 scales far better with more drives. Only the acces time gets higher and thats the only downfall in performance.

[Serra]

This is so not true. Raid 0 scales far better with more drives. Only the acces time gets higher and thats the only downfall in performance.

What part do you have a particular issue with? The theoretical changes were just plain math, and the fact is that 4 disks vs. 3 disks (for example) *cannot* offer more than a 9% speed increase... which isn't really that high. Once you shave off a percent or two for overhead (and yes, this will depend on hardware setup).. yeah, that's mid to low single digits. If you have a method of math that suggests otherwise I would be interested to see it.