[OpenIndiana-discuss] Recommendations for fast storage

[Edward Ned Harvey (openindiana)]

> From: Sašo Kiselkov [mailto:skiselkov.ml at gmail.com]
> 
> If you are IOPS constrained, then yes, raid-zn will be slower, simply
> because any read needs to hit all data drives in the stripe. 

Saso, I would expect you to know the answer to this question, probably:
I have heard that raidz is more similar to raid-1e than raid-5.  Meaning, when you write data to raidz, it doesn't get striped across all devices in the raidz vdev...  Rather, two copies of the data get written to any of the available devices in the raidz.  Can you confirm?

If the behavior is to stripe across all the devices in the raidz, then the raidz iops really can't exceed that of a single device, because you have to wait for every device to respond before you have a complete block of data.  But if it's more like raid-1e and individual devices can read independently of each other, then at least theoretically, the raidz with n-devices in it could return iops performance on-par with n-times a single disk.