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RAID-1 Mirror (SoftRAID, Thunderbolt v1)
Tests shown here uses the fastest portion of the drives in order to show the peak speeds possible with the Thunderbay; all hard drives slow down as they fill up, as per the simple physical fact of πD (track circumference).
The Thunderbay performed admirably, as did the Toshiba MG03ACA300 hard drives, which offer very impressive performance.
Tested with the Thunderbay IV (Thunderbolt, not Thunderbolt 2).
Results shown are real-world throughput through the file system API (not unachievable driver-level throughput).
This 4-way mirror is an interesting test of bus bandwidth, because software RAID-1 mirror means the driver has to send four copies of the data when writing, one to each drive. So a write speed of 180MB/sec really means that 720 MB/sec is going out over the bus. The performance see here thus has to be considered excellent.
For writes, performances is identical with 2/3/4 drives. But for reads, a benefit is obtained by reading from more than one drive. Throughput is not nearly so fast as RAID 0 striping, but it is of significant benefit for reads and is about all that can be expected from a mirror.
Those looking for high fault tolerance might find a 3-drive RAID-1 mirror a highly appealing setup, since it delivers read speeds quite satisfactory for even fairly demanding tasks.
RAID 1 X 4: 180 / 336 write/read MB/sec (four drives)
RAID 1 X 3: 181 / 278 write/read MB/sec (three drives)
RAID 1 X 2: 182 / 192 write/read MB/sec (two drives)