Raid zero ssd is slower because it doubles the seek latency..
It's so negligible that the gains on your read and writes out weighs the loss in seek latency.
Here's a little snippet I found:
"the hard disks performance is primarily determined by its latency,which is on the order of 10ms,vs .1ms for the SSD.If the SATA host adapter introduces a ms of latency,and the RAID bios introduces another ms,then its still a major win. Your seek times halve and transfer rates double,so your seek goes down to 10+1+1=12 ,halved=6ms. And your peak transfer rate is a GB/s. SO two disks is almost twice as fast. But the SSD has a seek latency on the order of .1ms,so your latency with a single drive is 1.1ms. But with the raid,its 2.1ms/2 or 1.05ms,which is hardly better than one,although your transfer rate is doubled. But thats not the whole story,because really,with the raid bios,your writes have more overhead than your reads. Say,2ms instead of 1. So lets say writes happen 25% of the time to 75% reads, Then still,the hard disk arrays average latency is 6.25ms. Still a vast improvement,and the difference in overhead is hardly noticeable. Even doing all writes,its 7ms. You'll never notice that at all. But for the SSD,its 1.05ms average latency 75% if the time,and 1.55ms latency 25% of the time, or 1.05*.75+1.55*.25=1.175ms. So the latency to access the disk,assuming our assumptions are met, INCREASES by around 7%. But if the system has to write a lot more than I assumed,like if its booting up,rebuilding the page files and the prefetch folder and superfetch cache,etc,then its going to be far worse. If it did 100% writes,the seek latency would increase to 1.55ms,a drop in seek time of nearly 41%. And we know that windows performance in fact is impacted HEAVILY by write latency. Just look at what a readyboost cache on a USB stick can do for you. Even at the low data rate of a flash drive,the low latency can make a big difference. "
