January 23rd, 2015

vantid

HP SSD Smart Path not always a smart choice

Inkbunny uses one of HP's RAID controllers. I've gotten intimately familiar with it over the past week while transforming Inkbunny's submissions array to RAID 5. It's pretty sweet.

I recently found out about a new feature it supports called SSD Smart Path. Unfortunately, for our purposes, it's not all that smart to use it.

One of the way RAID is meant to help is that it gives you more I/O operations per second (IOPS) by ganging together multiple drives using a dedicated processor. However, many enterprise SSDs are capable of so many IOPS that this system becomes a bottleneck when you place large numbers of them together in an array.

The solution? Rewrite the driver so that reads go almost directly to the disk, bypassing the RAID stack as far as possible.



Sounds sweet. Here's the problem: *It disables the RAID write cache on your SSDs, which may be slow at writes*.Collapse )
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