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ramonsmits merged 2 commits into from
Sep 11, 2026
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Document how to disable prefetching #8479

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Document how to disable prefetching
mauroservienti Sep 1, 2026
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Update servicecontrol/servicecontrol-instances/hardware.md
mauroservienti Sep 11, 2026
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11 changes: 11 additions & 0 deletions servicecontrol/servicecontrol-instances/hardware.md
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Expand Up @@ -92,3 +92,14 @@ Updating the full-text index requires a considerable amount of CPU and disk spac

- Turn off the 'FULL TEXT SEARCH ON MESSAGE BODIES' in the settings configuration of ServiceControl Management Utility
- Modify the [ServiceControl.Audit/EnableFullTextSearchOnBodies](/servicecontrol/audit-instances/configuration.md#performance-tuning-servicecontrol-auditenablefulltextsearchonbodies) setting in the configuration file

### Disable RavenDB document prefetching

## Persistently high disk I/O levels on audit instances

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mauroservienti marked this conversation as resolved.
> [!NOTE]
> Starting with ServiceControl Version 6.20.0, prefetching is disabled by default.

Audit instances with full-text indexing and message expiration enabled, and affected by constant high throughput on the audit queue, might show persistently high disk I/O levels. Some of the I/O is caused by document prefetching to optimize query performance. Considering that, under those premises, there is a disproportionate amount of I/O time dedicated to writes, it is better to disable prefetching by setting the system-wide environment variable `RAVEN_Storage_EnablePrefetching` to `false`. Once set, restart the ServiceControl instances.
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Once instances have been restarted, validate the setting has been applied by going to instance settings -> Database Settings -> Filter by `EnablePrefetching`, the reported value is `false`.