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4D SSD Watch: Benchmarking RAID 0 SSD's

by Josh Fletcher

Following up on my last blog post, and also on some of the information I presented in the 4D Summit 2011 Pre-Class, I've updated one of my systems to an Intel 7-series motherboard and benchmarked a RAID 0 SSD array. Read on for the results!


Last time I reported that Intel had added TRIM support for RAID 0 SSD arrays using 7-series-based motherboards. This is a critical feature to have for SSD's, so it was good news indeed.  Since then I've updated one of my systems to an Intel 7-series motherboard (ASRock z75 Pro3), RAID'ed my OCZ Vertex 3 120 GB SSD's and checked out the results with the popular ATTO benchmark.


For context I have added the results I presented at 4D Summit 2011.



The Raptor is a 10,000 RPM "enthusiast" HDD.  It was quite impressive in the days before SSD's. As the scale of this graph implies, that's no longer the case.


ATTO results for Western Digital Raptor 150



The Vertex 3 is a "second generation" SSD. The primary differentiator for second gen SSD's is support for SATA III, doubling the bandwidth from 3 GB/s (SATA II) to 6 GB/s. Here are the results I presented at the Summit for a single Vertex 3:


ATTO results for OCZ Vertex 3 120 GB



I'd actually purchased a second Vertex 3 quite a while ago in anticipation of RAID'ing them but always held off because of the lack of TRIM support. I mention this because there's actually nothing stopping you from RAID'ing any SSD.  It will work and you will get numbers like this, at least for a while.  The performance degredation you get without TRIM doesn't occur until the drive is nearly full. But with TRIM support there's no looking back!


ATTO results for RAID 0 OCZ Vertex 3 120 GB



It's amazing how SSD's can completely saturate the drive I/O channel. What happens with a second drive? Oh, you know, only double the bandwidth!  It's funny to see manufacturers selling SATA III HDD's; the drive will never saturate a SATA II channel, let alone SATA III (but I'm sure they enjoy charging extra for it!)


It is too bad Intel hasn't seen fit to get this working in any other configuration than RAID 0. Some redundancy would definitely be nice.  On the other hand, for double the performance, and with the falling cost of SSD's, RAID 0 is pretty compelling.


Because this is a 4D-related blog, it is important to acknowledge that these numbers reflect sequential performance. As we've mentioned in the past the most important metric for 4D applications is usually random I/O, not sequential. While RAID brings amazing sequential performance to SSD's it doesn't do much for random I/O. Still sequential throughput helps for things like making backups, copying the database to other locations, and installing updates. RAID 0 is still something worth looking at.

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