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HighPoint RocketRAID 2680 SAS/SATA RAID PCIe Host Adapter versus 'sister' RR4320

Originally posted December 11th, 2008, by rob-ART morgan, mad scientist

The HighPoint RocketRAID 2680 is designed to support up to 8 SAS or SATA drives. Though that's the same number of drives as the RocketRAID 4320 supports, the maximum bandwidth rate is different as you will see in the graphs below. To demonstrate the difference in performance you can expect from both SAS/SATA RAID host adapters, we tested both 4 and 8 drive configurations using both 15K SAS and 7K SATA drives.

It's important to note that when we used 8 drives, 4 of them were external. That was made possible through the use of external enclosures and an internal mini-SAS to external mini-SAS adapter. More on that later.

For this round, we used Disktester's Area Test defining a 4GB test file, 128MB chunk size, and 5 iterations. We sampled the RAID volume at 0% (empty) and at 90% (almost full). Though we have also tested with Kona System Test, we've learned from past experience that the results from DiskTester are essentially the same. In other words, DiskTester is very predictive of real world capture and playback of HD video, the most demanding streaming requirement.

SAS = Seagate Cheetah 15K.6 450G or 146G SAS drive
SATA = Samsung Spinpoint F1 7k 1000GB 3G SATA drive (HD103UJ)
COMBO = four SATA + four SAS drives
RR4320 = HighPoint
RocketRAID 4320 SAS/SATA RAID x8 PCIe host adapter
RR2680 = HighPoint
RocketRAID 2680 SAS/SATA RAID x4 PCIe host adapter.

1. As you can see, the RocketRAID 2680 has a throughput limit of just over 500MB/s. That may not be an issue for you if your target speed is under that rate. Or to put it another way, if you need a faster transfer speed than 500MB/s even when the volume is full, you should consider the RocketRAID 4320 which has a throughput rate of over 1000MB/s and uses the Intel IOP348 running at 1.2GHz.

Note that the RR2680 hangs tough versus the R4320 as long as you only have four SATA drives. The RR2680 falls behind when you connect five or more drives. You'll will also need more than four drives to maintain 500MB/s+ when the RAID volume starts filling up.

Another difference is RAID support. The RR2680 supports RAID 0, 1, 5, 10, and JBOD. The RR4320 supports those same modes plus it adds RAID 3 and 6.

And, of course, there's the cost difference: RR2680 typically sells for $300 while the RR4320 typically sells for $600. Both cards are cheaper and significantly faster than the $800 Apple Pro RAID card.

2. I must continue to emphasize that the transfer speed will drop as the RAID volume fills up -- especially if the drives used in the RAID volume are already bumping up against their maximum transfer rate. On the other hand, if the drives are "loafing" due to other throughput contraints (RAID type, host adapter limits), then you might be able to maintain the same speed when the volume is full as you saw when it was empty.

3. In our test, we used both the lower cost 7K SATA drives and the expensive 15K SAS drives. You have to factor in your budgeting limitations, target speeds, and your capacity needs when choosing which kind of drives to purchase. For example, the 15K SAS drives we used were 50% faster than the 7K SATA drives, but the SATA drives stored more than twice as much at a fraction (1/8) of the cost.

4. Neither HighPoint SATA/SAS RAID card is full length. That means you will need an extender cable to connect it to the mini-SAS connector on the Mac Pro motherboard. We used the MaxConnect extender from MaxUpgrades.

5. There are kits which will enable you to install more than four drives inside your Mac Pro. However, we decided to use external enclosures from both CRU-DataPort and Burly Storage to enable our eight drive testing. Since both mini-SAS connectors on the RocketRAID 2680 and 4320 are internal, you'll need an adapter similar to the one we ordered from PC-Pitstop that converts one or both of the internal connectors to external connectors.

6. Remember SCSI "voodoo"? Welcome to SAS voodoo! We learned in our testing that Mini-SAS adapters and cabling come in both straight and crossover wiring patterns. Some RAID Controllers require one or the other depending on the ports they use. Normally, if the RAID Card has external Mini-SAS ports you would use a straight symmetric external cable, then a crossover adapter on the backplane of the enclosure, and straight fanout cables inside the enclosure to go to the drives or back of the bays. It gets complicated. The crossover adapter or cabling is used to keep interference at bay. If you use one crossover adapter you also must use either a crossover cable or another adapter to counteract the wiring pinout. Confused? Consult your SAS dealer for assistance on purchase of the correct combination of adapters, cables, and enclosures. (Our thanks to Brian Adams of Burly Storage for explaining this to us.)

NOTES ON BOOTING OS X from a RR2680 or 4320 volume
To boot OS X from a RAID set or single drive initialized on the RocketRAID, you can't install the OS the "normal" way using the installer DVDs. You must use Carbon Copy Cloner (or similar app) to clone a normal boot drive (connected to a FireWire 800 enclosure in our case). Before doing that, use the browser based RAID Manager to install the latest EFI update from RocketRAID's download page for the appropriate card on the HighPoint Mac site.

Many of you are expressing a desire to boot from a RAID set plus have a dedicated data RAID set. With eight drives and the RocketRAID 2680 or 4320, that's easily done since it supports more than one RAID set.

Seagate makes the 15K SAS drives we used: the "screaming" Cheetah 15K.6 450G SAS drive -- a single unit clocks out at 160+MB/s. We also tested the 146GB version which we found to be 10% slower than the 450GB version.

Samsung makes the 7K SATA drive we used for testing. It's the 1TB Spinpoint F1 (HD103UJ) that we measured at 107MB/s in single drive form. As you can see above, the 15K SAS drive is 50% faster.

Since the RocketRAID 2680 and 4320 are not a full length cards, they need to connect to the mini-SAS connector on the Mac Pro motherboard in order to work. Enter MaxUpgrades with a SAS cable extender. Check with your host adaper dealer for the proper extender.

The CRU-DataPort SAS enclosure made it easy to add up to for external SAS drives to our four internal SAS drives. It is rugged with a choice of two different styles of drive trays. It features dual cooling fans. Though the fan frequency was not obtrusive, the amplitude was between 57-60dB. We would like to see that be more like 45dB, the typical noise level of the Mac Pro test unit.

For our four external SATA drives, we tested with the Burly Storage SATA enclosure with "trayless" bays. It uses a single mini-SAS connector to mate with the Mac Pro.

Because the RocketRAID 2680 and 4320 feature two internal mini-SAS connectors (and no external data connectors), we acquired an adapter from PC-Pitstop that converts one or both internal mini-SAS (8087) connectors to external mini-SAS connectors (8088). It is mounted in one of the PCIe slot openings. We ran a mini-SAS to mini-SAS cable from the host adapter to the "in to out" adapter. Once that was installed and connected, we connected to the external SAS or SATA enclosure using the mini-SAS cable provided by the vendor.

Apple Online Store

The RocketRAID 2680 and RocketRAID 4320 are not sold directly by HighPoint Technology. Check with these Mac friendly resellers to order:


WHERE TO BUY THE mini-SAS Extender Cable
MaxUpgrades sells the MaxConnect SAS/SATA link (adapter/extender) that we used. Your HighPoint dealer may also have their own extender cable and coupler.

PC PitStop has all the SAS cables and adapters you can imagine. We used a particular one to convert an internal SAS host adapter to external. See their decision matrix for SFF-8087, SFF-8088 and SFF-8470.

The Seagate Cheetah 15K.6 SAS drive is in stock at Other World Computing.
The Hitachi Ultrastar 15K SAS drive is in stock at Trans International

SATA drives work with the RocketRAID 2680 and 4320. They may be fast enough for your purposes and certainly cost a lot less than 15K SAS drives.

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2008 Rob Art Morgan
"BARE facts on Macintosh speed FEATS"
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