[CI] MergeWithLowDiskSpaceIT testRelocationWhileForceMerging failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #10009 / ubuntu-2404-aarch64_checkpart1_platform-support-arm
• elasticsearch-periodic #9991 / encryption-at-rest
• elasticsearch-periodic-platform-support #10002 / ubuntu-2204_platform-support-unix
• elasticsearch-periodic-platform-support #9995 / windows-2025_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #9988 / opensuse-leap-15_platform-support-unix
• elasticsearch-periodic-platform-support #9981 / amazonlinux-2023_platform-support-aws
• elasticsearch-periodic #9970 / concurrent-search-tests
• elasticsearch-periodic-platform-support #9974 / windows-2025_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #9967 / opensuse-leap-15_platform-support-unix
• elasticsearch-periodic-platform-support #9960 / oraclelinux-9_platform-support-unix

Reproduction Line:

./gradlew ":server:internalClusterTest" --tests "org.elasticsearch.index.engine.MergeWithLowDiskSpaceIT.testRelocationWhileForceMerging" -Dtests.seed=F6B7B47914FF809 -Dtests.locale=sq-Latn-AL -Dtests.timezone=Africa/Tripoli -Druntime.java=24

Applicable branches:
9.0

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: 
Expected: <1>
     but: was <2>

Issue Reasons:

• [9.0] 40 failures in test testRelocationWhileForceMerging (7.4% fail rate in 540 executions)
• [9.0] 3 failures in step ubuntu-2404-aarch64_checkpart1_platform-support-arm (13.6% fail rate in 22 executions)
• [9.0] 3 failures in step single-processor-node-tests (14.3% fail rate in 21 executions)
• [9.0] 3 failures in step concurrent-search-tests (15.0% fail rate in 20 executions)
• [9.0] 2 failures in step rhel-8_platform-support-unix (9.5% fail rate in 21 executions)
• [9.0] 3 failures in step rocky-8_platform-support-unix (14.3% fail rate in 21 executions)
• [9.0] 2 failures in step oraclelinux-9_platform-support-unix (9.5% fail rate in 21 executions)
• [9.0] 2 failures in step debian-12_platform-support-unix (9.5% fail rate in 21 executions)
• [9.0] 2 failures in step opensuse-leap-15_platform-support-unix (9.5% fail rate in 21 executions)
• [9.0] 2 failures in step rhel-9_platform-support-unix (9.5% fail rate in 21 executions)
• [9.0] 2 failures in step sles-15_platform-support-unix (9.5% fail rate in 21 executions)
• [9.0] 4 failures in step amazonlinux-2023_platform-support-aws (19.0% fail rate in 21 executions)
• [9.0] 4 failures in step windows-2025_checkpart1_platform-support-windows (19.0% fail rate in 21 executions)
• [9.0] 2 failures in step windows-2022_checkpart1_platform-support-windows (9.5% fail rate in 21 executions)
• [9.0] 19 failures in pipeline elasticsearch-periodic-platform-support (86.4% fail rate in 22 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

This has been muted on branch main

Mute Reasons:

• [main] 5 failures in test testRelocationWhileForceMerging (35.7% fail rate in 14 executions)
• [main] 4 failures in step part-1 (36.4% fail rate in 11 executions)
• [main] 4 failures in pipeline elasticsearch-pull-request (40.0% fail rate in 10 executions)

Build Scans:

• elasticsearch-periodic #9552 / single-processor-node-tests
• elasticsearch-pull-request #82387 / part-1
• elasticsearch-pull-request #82388 / part-1
• elasticsearch-pull-request #82379 / part-1
• elasticsearch-pull-request #82371 / part-1

[elasticsearchmachine]

Pinging @elastic/es-distributed-indexing (Team:Distributed Indexing)

[elasticsearchmachine]

This has been muted on branch 9.1

Mute Reasons:

• [9.1] 2 failures in test testRelocationWhileForceMerging (22.2% fail rate in 9 executions)

Build Scans:

• elasticsearch-periodic-platform-support #9667 / rhel-9_platform-support-unix
• elasticsearch-pull-request #82359 / part-1

[elasticsearchmachine]

This has been muted on branch main

Mute Reasons:

• [main] 24 failures in test testRelocationWhileForceMerging (6.2% fail rate in 387 executions)
• [main] 2 failures in step debian-12_platform-support-unix (33.3% fail rate in 6 executions)
• [main] 8 failures in step part-1 (4.7% fail rate in 171 executions)
• [main] 2 failures in step ubuntu-2404-aarch64_checkpart1_platform-support-arm (40.0% fail rate in 5 executions)
• [main] 7 failures in pipeline elasticsearch-pull-request (4.2% fail rate in 168 executions)
• [main] 5 failures in pipeline elasticsearch-periodic-platform-support (83.3% fail rate in 6 executions)
• [main] 2 failures in pipeline elasticsearch-periodic (40.0% fail rate in 5 executions)

Build Scans:

• elasticsearch-periodic-platform-support #9696 / debian-12_platform-support-unix
• elasticsearch-pull-request #83338 / part-1
• elasticsearch-periodic-platform-support #9682 / almalinux-8-aarch64_checkpart1_platform-support-arm
• elasticsearch-periodic-platform-support #9675 / ubuntu-2404-aarch64_checkpart1_platform-support-arm
• elasticsearch-periodic-platform-support #9675 / oraclelinux-9_platform-support-unix
• elasticsearch-periodic-platform-support #9668 / windows-2022_checkpart1_platform-support-windows
• elasticsearch-periodic #9657 / release-tests
• elasticsearch-pull-request #82401 / part-1
• elasticsearch-pull-request #82396 / part-1
• elasticsearch-pull-request #82388 / part-1