DAOS-18825 pool: include excluded ranks as DOWNOUT at creation time - #18994
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DAOS-18825 pool: include excluded ranks as DOWNOUT at creation time#18994wangshilong wants to merge 1 commit into
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Ticket title is 'Imbalanced object distribution for G32 oclass in pool with asymmetric fault domain topology' |
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DAOS placement uses consistent hashing to distribute data across nodes and fault domains. In theory, each node/domain should have the same probability of being selected for data placement, which helps ensure balanced data distribution. However, pool create currently filters out excluded ranks and only creates VOS pools on alive ranks. If a node has only one alive rank, this can cause data imbalance. To address this, pool create now sends DOWNOUT ranks to the PS leader. VOS pools are still created only on alive ranks, but DOWNOUT ranks are included in the pool map. During layout calculation, placement remaps data from DOWNOUT ranks onto alive ranks, reducing imbalance. After reintegration, data can be moved back to the reintegrated ranks. Features: rebuild pool Signed-off-by: Wang Shilong <shilong.wang@hpe.com> Signed-off-by: Xuezhao Liu <xuezhao.liu@hpe.com> Co-authored-by: Xuezhao Liu <xuezhao.liu@hpe.com>
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wangshilong
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September 7, 2026 02:31
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knard38
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tanabarr
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Test stage Functional Hardware Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-18994/3/execution/node/1672/log |
liuxuezhao
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Test stage Functional Hardware Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-18994/4/execution/node/610/log |
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ftest changes LGTM (they match what is in master)
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DAOS placement uses consistent hashing to distribute data across nodes and fault domains. In theory, each node/domain should have the same probability of being selected for data placement, which helps ensure balanced data distribution.
However, pool create currently filters out excluded ranks and only creates VOS pools on alive ranks. If a node has only one alive rank, this can cause data imbalance. To address this, pool create now sends DOWNOUT ranks to the PS leader. VOS pools are still created only on alive ranks, but DOWNOUT ranks are included in the pool map. During layout calculation, placement remaps data from DOWNOUT ranks onto alive ranks, reducing imbalance. After reintegration, data can be moved back to the reintegrated ranks.
Features: rebuild pool
Steps for the author:
After all prior steps are complete: