As you may have noticed, I have installed a ICYBOX IB-RD2262 USEb on my MacBook Pro. It contains two 500GB SATA disks. You can either use the “RAID Master” provided tools to create the RAID system or use the Mac OS X native RAID system. The main difference is that, using RAID Master, you’ll only see the rendered RAID disk in “Disk Util” ; whereas you will see both disks and the RAID system if you use the standard OS X configuration.
I wanted to check if there were any performance difference between native OS X configuration and RAID0/SPAN using RAID Master. Maybe using RAID Master, you benefit some hardware RAID system…
What I did is configure:
- A Seagate ST9500325AS 500GB SATA 3Gb/s 5400RPM 8MB ;
- A Western Digital WD5000BEVT 500GB SATA/300 5400RPM 8MB ;
- Mac OS X, RAID0 with 32KB stripes ;
- RAID Master, RAID0 ;
- RAID Master, SPAN.
There are several things that puzzles me…
First of all, SPAN configuration should be way slower than RAID0 ; as it should write to only one disk at a time where RAID should parallelize the writes on both disks…
Then, I expected the “RAID Master” configuration to be faster, because using some kind of hardware to deal with the RAID…
I use “Disk Speed Test” to check the “RAID Master RAID0” configuration. I’m not sure of what it says… There are lots of values that goes from 75 to 2 MB/s… But if I only consider the “big button values”, this configuration is supposed to achieve 63MB/s in writing mode and 75MB/s in reading mode ; which is quite in the range of what I got using iostat.
According to the Firewire-800 standard, the maximum speed I could reach is about 786Mbps ; that’s about 98MB/s. My results are not so far from that… I begin to think my similar results are more due to the single FW800 link than any other aspects of the RAID configuration.
I found a test on my disk enclosure. What I was looking for is this: “(…) Using the FireWire 800 port of a Digitus PCI adapter, we measured an average read rate of 62 MB/s, typical for a Windows computer (…)”. Same as what I found.
That would probably be nice to test multiple concurrent read/write access in those RAID mode. But it seems any of the modes can be use without any performance loss. It also looks like this enclosure is not be used for faster access (2 disks rather than a single) rather than concatenating or protecting “low” size disks. Which is not bad as this is why I bought it :D Should you want better performance, the eSATA port is still available (on the enclosure, not the MBP ;)