HCSEC-001-MARCH-2026 [PERFORMANCE]
I/O Delay During FSTRIM Execution on VPS
Status: Identified
Severity: Low
Category: Performance
First Observed: February 2026
Last Updated: March 2026
Affected Services: Limited number of VPS instances using specific hardware emulation profiles (NVMe and HDD RAID tiers)
Summary
Following the upgrade to Proxmox VE 9.1, isolated reports indicated that in some cases, execution of fstrim within a VPS may result in a temporary increase in I/O wait on the underlying storage subsystem.
Initial analysis suggested no consistent pattern. Further investigation has now identified that the behavior is associated with a specific virtual machine hardware emulation profile.
Impact
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Temporary increase in I/O wait (observed in the ~20–25% range in isolated cases)
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Short-lived performance fluctuation during trim operations
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No data integrity risk identified
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No persistent degradation observed
Customer Impact
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Impact affects a very limited number of VPS instances
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Performance impact is limited to the duration of trim execution
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No action is required from customers
Findings
Investigation has determined that affected VPS instances are those configured with the Q35 machine type (hardware emulation profile).
Systems using alternative emulation profiles do not exhibit this behavior under similar conditions.
Resolution
HOST-C is currently evaluating mitigation options, including controlled migration of affected VPS instances to a different hardware emulation profile where the issue is not observed.
All potential changes are being assessed to ensure compatibility, stability, and no disruption to customer workloads.
Further updates will be provided once a final resolution approach is confirmed.
Closing Statement
This issue is limited in scope, does not impact data integrity, and is being handled as part of ongoing performance optimization efforts.
— HOST-C Network
"Storage by Design"
