Maxtor DiamondMax 10: Exploring NCQ & RAID
RAID Testing (32K Stripe)
A 32K stripe size is default for several of today's popular RAID configurations and represents a fair middle ground in the available sizes ranging from 4K to 128K. The 32K stripe size is available in all configurations and provides a good baseline to measure RAID performance.
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Clearly, the number of drives used is a significant factor in RAID performance. Adding the third drive to the Maxtor stripe set increases capacity by 50% and read performance by 45%. An interesting item to note is that when adding a third drive to the pair of RAID 0 Maxtor drives and the array is configured in RAID 5, both the capacity and performance are nearly identical. A third Raptor was not available at the time of testing to see if the performance/capacity pattern was drive independent.
For write performance in RAID 0 modes, the pattern is consistent with the read performance. Adding the third drive to the RAID 0 set has a more pronounced impact on write performance, and with a 50% increase in capacity comes a 61% increase in performance. The story is very different with the RAID 5 array where write performance is dramatically reduced by the parity calculation overhead. In RAID 0, the three Maxtor drives are about 6% faster in write operations. In RAID 5, the three Maxtor drives are over 80% slower in write operations.
Similar to the pattern seen in the single drive configurations, the NCQ enabled DiamondMax drives really start to shine in burst measurements. When the conditions are right for NCQ to perform, the numbers clearly show the impact. In two drive RAID 0 configurations, the Raptors are 24.9 MB/s faster in sustained read over the pair of Maxtors. For burst performance, the same configuration of Maxtors are 22.6 MB/s faster than the Raptors. In burst performance, the addition of a third drive to the Maxtor RAID 0 set does not have as pronounced of an impact, but still turns in an impressive number of 316.2 MB/s. This is more than twice the theoretical bus transfer rate of a single Maxtor drive.
