While benchmarking a new Windows Server file server, an administrator notices small-block write latency is three to four times higher than on identical systems. The administrator confirms the six-disk hardware RAID-5 set shows an Optimal status with its write-back cache enabled, and that no rebuilds or background tasks are running on the array. A review with DiskPart reports that the system volume begins at an offset of 32,768 bytes (sector 64), and the RAID controller uses a 256 KB stripe unit.
Which of the following is the MOST likely reason for the poor disk performance?
The file system was formatted with a 64 KB allocation unit size, leading to wasted space and high latency.
The partition is misaligned with the 256 KB stripe size, causing each write to span multiple stripes and trigger read-modify-write operations.
The controller's battery-backed cache is in learning mode, temporarily disabling write-back caching.
The array is still completing an online capacity expansion, so I/O is throttled until the process finishes.
Because the first partition starts at a 32 KB offset (64 × 512-byte sectors) that is not an even multiple of the 256 KB stripe unit, every write request that crosses a file system cluster boundary is likely to span two RAID stripes. For RAID-5 this forces the controller to perform extra read-modify-write cycles, dramatically increasing latency even though the array itself is healthy. Aligning the partition to a 256 KB (or more commonly, a 1 MB) boundary would eliminate the unnecessary I/O and restore normal throughput.
The other options do not match the symptoms given:
A battery learning cycle or disabled cache would be reported in the controller logs. The scenario also states the cache is enabled.
An online capacity expansion would show as a running background task, which the scenario explicitly states is not occurring.
Using a 64 KB NTFS allocation unit may waste space on small files but does not by itself create extra read-modify-write operations at the RAID level.
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