Fix the warm up cache issue

[LAVEEN]

The integration test failure was caused by a cold cache miss during the FIO performance benchmark:

The test validates GCS Anywhere Cache (Rapid Cache), which is an SSD-backed zonal read cache.
Anywhere Cache is demand-driven and uses the admit-on-first-miss policy, meaning data is only loaded into the high-speed cache after it has been read for the first time.
The test file (/data/fio) is newly written during the test. Writing the file does not populate the read cache.
The benchmark ran a random-read test (--rw=randread) with small 4K blocks across the 1G file immediately after creation.
Because the cache was completely cold, nearly 100% of these random reads missed the cache and had to fetch data directly from GCS. This resulted in typical GCS direct-access latencies (~10ms per I/O), leading to only 129 IOPS (threshold: >= 300) and 516 KB/s bandwidth (threshold: >= 1000 KB/s).

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a cache warm-up step to the FIO performance benchmark suite. By performing a sequential read of the test file before the actual latency test, the GCS Anywhere Cache is properly populated, preventing cache misses that previously caused the integration tests to fail due to high latency.

Highlights

• Cache Warm-up Implementation: Added a pre-test fio read operation to populate the GCS Anywhere Cache, ensuring subsequent performance benchmarks run against a warm cache.
• Test Stability: Addressed integration test failures caused by cold cache misses, ensuring performance metrics meet the required thresholds.

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[gemini-code-assist]

Code Review

This pull request introduces a warmup step using fio before running the main read latency tests in both the Kubernetes job template (fio-test-job.yaml.j2) and the Ansible playbook (test-slurm-rapid-storage.yml). Feedback suggests adding set -e to the multi-line container script in the Kubernetes job template to ensure that any failure during the warmup step causes the script to exit immediately rather than silently proceeding to the latency test.