rbarbati (5/2/2012)
This is a nice article, but possibly a bit dated and not really considering higher-end enterprise-scale subsystems that are available and more common these days, where RAID is not only obsolete, but not even a configuration option on the subsystem. Higher end arrays are now 'wide-striping' (as one term) across the entire array and are managed by the subsystem HW/FW/SW itself. Configuration is limited more to logical units and volumes. So although the discussion is valid for a more traditional physical server, I beleive more consideration needs to be placed on newer generation virtual compute modules with high-end disk subsystems. Also when reaching multi-terabyte/pedabyte scales, spindle counts are not much of a factor really either, each spindle possibly (typically) being a terabyte drive in itself. These systems are tuned and configured so differently than, say a local disk array, that I feel it warrants mention.
I suspect one of us needs to study "wide striping" in greater depth. As far as I'm aware based on a cursory inspection of the literature, "wide striping" is commonly using the very normal, standard RAID levels this article and discussion references, but with more drives. I.e. instead of a minimum 2+1 RAID 5 array, or even a normal 4+1 or 5+1 RAID 5 array, it's implementing an N+1 array, where N is "large". It's got all the normal features of a RAID 5 with many disks in the set; it averages out performance, it's got the write penalty, and it is resilient to only 1 drive failure at a time. When you put multiple workloads on the array, you get all the same features: when both Workload A and Workload B run at the same time, they compete for resources (and if everyone runs really big, long operations the first day of the quarter, perhaps they all take a lot longer), but when only one workload is active, it gets all the performance.
Reference: http://www.storagerap.com/2010/03/calculating-the-output-of-wide-striping.html
Reference: http://gestaltit.com/all/tech/storage/chris/enterprise-computing-the-wide-striping-debate/[/url]