Testing:
Testing the various RAID configurations was a fairly simple affair, a file was transferred to and from the array and the transfer times were recorded.
CentOS Linux 4.0 was rebooted prior to creating each RAID array using mdadm v2.2. Once each array was created, formatted, and mounted, a 321.7 MB file (id Software's Quake 4 Linux demo) was copied from a folder on the system's hard drive to the array. Once that stage was complete, the file was then copied from the RAID array back to a different folder on the system's hard drive.
The following configurations were tested using the basic procedure described above:
• Single Drive (WinXP)
• Single Drive
• 2 Drive Linear
• 2 Drive RAID 1
• 2 Drive RAID 0
• 4 Drive RAID 0
Except for the one configuration specifically indicated as "WinXP", all tests were conducted in CentOS Linux 4.0. One round of testing was conducted in Windows XP Professional as a point of reference. The chart below summarizes the read/write transfer times of all configurations tested (lower is better).
The numbers may look inconsistent (and they were), but a general confirmation of RAID performance can be seen. A four drive RAID 0 array was extremely fast, while a two drive RAID 0 array was moderatly faster than a single drive configuration. Getting just one succesful run for each RAID array was difficult enough, and only the single drive configurations were run multiple times for verification purposes.
The data in the next chart simply divides the file size by the transfer time in order to present a transfer rate (higher is better).
As you can see, if you could get a reliable set of drives (and drivers) to operate a four drive RAID 0 array, the performance would make it worthwhile. The single drive speed of these drives was not particularly impressive, making me think that an array of faster drives (perhaps the OCZ Rally) would be much better. On top of that, the reliability of these drives was terrible, and a set of high quality thumb drives might eliminate all of the struggles and second guessing I experienced.
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