PCIe SSDs, which combine a RAID chip with several SSD controllers and plenty of NAND flash onto one convenient and speedy package, are not a new idea. We’ve reviewed several, most recently the OCZ RevoDrive3 X2 in December 2011. They can be handy for people who want the speed of modern SSDs but don’t have free 6Gb/s SATA ports (this means you, X58). OWC’s Mercury Accelsior comes in sizes up to 960GB; we tested the 480GB version.
The Accelsior’s blades can be replaced with higher-capacity ones in the future, but will anyone actually do that?
The Accelsior is a low-profile PCB, so it can be used in small form factor machines or 1U servers. Unlike the RevoDrive, the Accelsior doesn’t require special drivers. The x4 PCIe 2.0 board contains a Marvell RAID controller, as well as two long, skinny SSDs in RAID 0, each with an SF-2281 controller and, on this model, eight 256Gb Micron synchronous NAND modules for a total of 240GB of usable space per blade.
We compared the Accelsior to a 480GB RevoDrive3 x2 as well as a RAID 0 of two 240GB SF-2281-based Vertex 3s. We saw sustained read speeds above 700MB/s and writes above 550MB/s in both CrystalDiskMark and AS SSD. This is quite a lot faster than any 6Gb/s SATA drive (which top out around 500MB/s), but the reads couldn’t match the more than 1GB/s reads from the Vertex RAID in AS SSD. Both the RevoDrive and the Vertexes had higher 4KB random IOPS at all queue depths, though the Accelsior’s maximum response time was the lowest of the three.
OWC states that you’ll be able to buy higher-capacity blades in the future, so you can upgrade the storage and keep the card. Since each blade contains the NAND and the controllers, future blades could even use different controllers. But given that you can’t reuse the blades anywhere else, will anyone want to just throw away perfectly good SSDs?
At $765, the Accelsior is a pricy way to get 480GB of RAIDed SandForce drives. If you have a RAID card or two free 6Gb/s SATA ports, you can get two top-notch 240GB drives for about $500, and have faster performance. But if the driverless convenience and upgrade potential intrigues you, the Accelsior is a great choice.
OWC Mercury Accelsior 480GB
Speedy, upgradeable; driverless; doesn’t take up SATA ports.
Pricier and slower than DIY; will anyone actually upgrade?
OWC Mercury Accelsior
OCZ RevoDrive3 x2
2x OCZ Vertex 3 (RAID 0)
Sustained Read (MB/s)
Sustained Write (MB/s)
Seq. Read (MB/s)
Seq. Write (MB/s)
4KB Read (IOPS)
4KB Write (IOPS)
64KB File Read (MB/s)
64KB File Write (MB/s)
4KB Random Write (IOPS)
Max Access Time (ms)
PCMark Vantage x64 HDD
PCMark 11 x64 SST
Best scores are bolded. Our test bed is a 3.5GHz Core i7-3770K processor on an Asus P8Z77 Premium running Windows 7 Professional 64-bit SP1. SATA controllers tested on Intel 6Gb/s ports with IRST 10.5.