LEGEND
HPT Quad = Four 6Gb/s SSDs in RAID 0 (striped) mode connected to the RocketRAID 2721
ATTO Quad = Four 6Gb/s SSDs in RAID 0 (striped) mode connected to the ExpressSAS R644
HPT Triple = Three 6Gb/s SSDs in RAID 0 (striped) mode connected to the RocketRAID 2721
ATTO Triple = Three 6Gb/s SSDs in RAID 0 (striped) mode connected to the ExpressSAS R644
HPT Dual = Two 6Gb/s SSDs in RAID 0 (striped) mode connected to the RocketRAID 2721
ATTO Dual = Two 6Gb/s SSDs in RAID 0 (striped) mode connected to the ExpressSAS R644
HPT Single = One 6Gb/s SSD connected to the RocketRAID 2721
ATTO Single = One 6Gb/s SSD connected to the ExpressSAS R644
The 240G 6Gb/s SSDs were SandForce SF-220 based (one from OWC, three from OCZ).
Test "mule" was a 2010 Mac Pro 6-core Westmere.
Both host adapters were in the x16 slot 2 (running at x8).
INSIGHTS
Notice the HighPoint RocketRAID 2721 was fastest on READs while the ATTO ExpressSAS R644 was fastest on WRITEs. Overall, both host adapters performed well but fell short of my fantasy of 2000MB/s for four 6Gb/s SSDs. If you need to go faster than the speeds we posted, you will need more than four 6Gb/s SSDs. (The RocketRAID 2721 uses the same driver as the RocketRAID 2722. Download the driver HERE.)
In a subsquent article, we achieved 3000MB/s using eight 6G SSDs. The HighPoint RocketRAID 2744 (a 16 lane card with four external mini-SAS ports) was used.
CAN YOU BOOT OS X?
ATTO's R644 will boot OS X if you flash it with the EFI64 flash update file from the Mac OS X Flash Bundle. After using Carbon Copy Cloner to clone our OS X boot drive to a triple SSD RAID set, we confirmed that the R644 does boot OS X. The HighPoint RR2721 (and 2722) does not have an EFI BIOS so it can NOT boot OS X.
If you are planning to boot from a RAID 0 array, you may not see any better performance than you would booting from a single SSD. That's because the RAID set can't do any more transactions per second than a single SSD. And the random small transfer rates are only slightly higher with two versus one. And three or four were no faster than two. The main reason for booting from a multiple 6Gb/s SSD RAID set would be for the extra storage capacity. You might consider booting from one 6Gb/s SSD and using a striped set of three or four to use as a scratch volume or working capture/playback volume.
DO THE CARDS MAKE THE MAC PRO NOISY?
The host adapters have heatsinks without fans, but ATTO overrides the Mac Pro's system fan management with their own fan speed controller. Problem is that it runs up the fans to full speed at all times regardless of the temperatures. We chose to remove it. We monitored temps and controlled fan speeds with smcFanControl. (Max PCI bay temp should not exceed 60C or 140F.) In our testing, the temps never came close to the max and we never had to tweak the fan speeds.
DETAILS: Host Adapters
We chose the ATTO ExpressSAS R644 and the HighPoint RocketRAID 2721 because both are 6Gb/s rated. Both have an internal mini-SAS port as well as an external mini-SAS port. Both are designed to support four internal drives and four external drives (in an enclosure). Both are 8 lane PCie 2.0 host adapters that support both SATA and SAS drives.
Officially, HighPoint only supports host adapters with external ports (RR2722 and RR2744) on the Mac Pro. As you can see from our test results, the RR2721 works fine on the Mac Pro using the RR2722 drivers. Caution when you buy unsupported "PC only" versions of the RocketRAID as you many not get tech support for it when using it on the Mac Pro. Though the ATTO ExpressSAS R644 costs significantly more than the HighPoint RocketRAID 2721 and 2722, it does boot OS X. Secondly, it gives you more setup and performance tweaking options for your RAID set. Thirdly, ATTO fully supports host adapters for the Mac Pro with internal ports.
Speaking of price, don't get seduced by the low cost single lane (x1) 6Gb/s host adapters. They may be adequate for HDDs, but SSDs will be hamstrung by the lower bandwidth. For example, our tests with a dual port x1 6Gb/s host adapter showed a maximum of 392MB/s READ speed and 220MB/s WRITE speed with two 6GB/s SSDs in a RAID 0 set. Compare that to the 1005MB/s READ speed and 949MB/s WRITE speed we saw with dual 6GB/s SSDs using the eight lane (x8) host adapters.
DETAILS: Enclosures
If you want to run the 6Gb/s SSDs externally, ideally you'll want a 6Gb/s rated enclosure or one with a "dumb straight-through" backplane. We have tested the 6Gb/s SSDs with the Stardom/Raidon ST8-U5 and the FirmTek SeriTek/2eEN4 enclosure. Both get the full speed out of the 6G SSDs. The easiest way to install an SSD in one of these enclosures is to convert it to 3.5 inch form factor with mounting holes. We used the Icy Docks sold by OWC. The newest silver metal Icy Dock works fine in the FirmTek two and four bay enclosures but the Stardom/Raidon ST8-U5 required the black plastic Icy Dock due to the fact that the newer metal version has a ridge in the back that keeps it from plugging into the ST8-U5 backplane.
DETAILS: Internal mounting options
If you want the 6Gb/s SSDs mounted internally to the Mac Pro and connected to the third party 6Gb/s host adapter, the installation is a bit more tricky. Placing the SSD inside an Icy Dock makes it easy to attach to any drive bay sled, but you'll need a custom sled that bypasses the data connector on the Mac Pro's backplane. We have successfully used two options. MaxUpgrades offers a "Backplane Attachment" kit which enables the SSD to pull power off the Mac Pro's motherboard while facing the data port down at a 90 degree angle to enable connection with the host adapter.
Another custom sled comes with the Trans International "Pro Cable - 1 Kit" which turns the SSD 180 degrees so the data and power connectors face outward. Again, the idea is to bypass the built-in data connection and connect to the 6Gg/s PCIe host adapter. This kit also provides power cables.
DETAILS: Cables
Finally, you will need to provide a data connection between the 6Gb/s SSD and the 6Gb/s host adapter. Since both the ATTO and HighPoint adapters use a mini-SAS connector externally and internally, you'll need a cable with the appropriate connector(s). We connected the ST8-U5 enclosure to the host adapter using a mini-SAS to mini-SAS cable (SF-8088 to SF-8088). For the FirmTek SeriTek/2eEN4 enclosure, we used a mini-SAS (SF-8088) to four eSATA fan out adapter cable. For the internal setup, we used a mini-SAS (SF-8087) to four SATA fan out adapter cable like this one sold on NewEgg.
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