if i understand that paper correctly, using stacked striped metaLUN may not be an issue for heavy random io profile. Maybe John can comment on that but i guess the safest bet not to do that.
CX3-20  So I have a high performance raid group,6 disks in raid 10.  When it was originally layed out, there was just on 146 GB Lun(lets call it lun 50) created, leaving the other 254GB unallocated.  Now of course, after 2 years, we need to expand our LUN 50 and would like to utilize the empty space in the raid group... only now we see the problem in expanding.  It seems like in order to expand, we would need to create new LUNS in that raid group and Metalun them together.   So here's the problem.            It seems like either way, Concat, or stripe, we would take a performance hit due to the fact that any lun we used to expand would be in the same raid group(thusly the same disks, only stacked on top of one another).   Does this assumption sound correct?            If we created a new lun of  146GB in the raid group, then striped them together, when data was accessed would there be a performance loss due to the stacking of luns on the same disk, or does the striping take care of this.  I've included some images just to help illustrate.  The first is the current config, the second is the proposed.  Expanding into luns in the same raid group just seem like it would cause issues.  Or does the array just take care of this through magic, and the performance hit is just in our imagination? [IMAGE]  [IMAGE]
Expand Lun, use unused space in same raid group?