Performance Comparisons Based On Platter Speed - HP 418371-B21 - Dual Port 72 GB Hard Drive Technology Brief

Performance comparisons based on platter speed

The charts in Figure 7 compare sequential read performance between 10K (rpm) and 15K SFF SAS
drives operating as a 6-drive array with an HP Smart Array P800 controller using RAID 5. Charts 7A
through 7E show the drive array performance for sequential reads per block size at a specific queue
(Q) depth. Queue depth is the number of commands waiting to be serviced by the storage system. In
workstations and small server systems queue depth rarely exceeds 1, but in an enterprise server
environment a large number of users generating requests can result in a queue depth of tens or
hundreds. Chart 7F shows random read IOPS performance.
Figure 7. Performance comparison: 10K versus 15K RPM, RAID 5 controller and 6 SFF SAS drives
A: Sequential read, Q1 B: Sequential read, Q4
C: Sequential read, Q8 D: Sequential read, Q16
E: Sequential read, Q32 F: Random IOPS
10K RPM SAS HDD 15K RPM SAS HDD
As indicated by the charts, 15K drives show a significant advantage where the requested data blocks
are stripe size (64 KB) or larger. Although the IOPS rating can increase with greater queue depths,
user interaction response of the system is best when the queue depth remains below 32.
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