SG0-001 · Question #356
An administrator has 4 SAS drives that the manufacturer lists at 140 IOPS. How many IOPS combined would these drives have in a single RAID 0+1?
The correct answer is C. 560 Read or 280 Write IOPS. In a RAID 0+1 configuration with 4 drives, read performance benefits from striping across all drives, while write performance is affected by mirroring, effectively using half the drives for writes.
Question
An administrator has 4 SAS drives that the manufacturer lists at 140 IOPS. How many IOPS combined would these drives have in a single RAID 0+1?
Options
- A140 Read or 140 Write IOPS
- B280 Read or 140 Write IOPS
- C560 Read or 280 Write IOPS
- D560 Read or 560 Write IOPS
How the community answered
(62 responses)- A8% (5)
- B16% (10)
- C73% (45)
- D3% (2)
Why each option
In a RAID 0+1 configuration with 4 drives, read performance benefits from striping across all drives, while write performance is affected by mirroring, effectively using half the drives for writes.
This option represents the performance of a single drive, not a combined RAID array, and significantly underestimates the capabilities.
This option incorrectly calculates write IOPS; a RAID 0+1 with 4 drives has 2 effective drives for writes, not 1, and misrepresents the read performance.
A RAID 0+1 (RAID 10) configuration with 4 drives consists of two mirrored pairs, each striped. For reads, all 4 drives can serve data, yielding 4 * 140 = 560 Read IOPS, while for writes, data is mirrored across pairs, effectively using only half the drives for write performance, resulting in 2 * 140 = 280 Write IOPS.
This option incorrectly suggests write performance is equal to read performance, which is not true for RAID 0+1 due to the overhead of mirroring data to both striped pairs.
Concept tested: RAID 0+1 (RAID 10) performance characteristics
Source: https://www.dell.com/community/Storage-Wiki/RAID-10-performance-considerations/ta-p/13010724
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