Performance Tweaks

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Yellowpin.svg Note: Article about Proxmox VE 2.0

Introduction

This page is intended to be a collection of various performance tips/tweaks to help you get the most from your virtual servers.

KVM

Disk Cache

Yellowpin.svg Note: The information below is based on using raw volumes, other volume formats may behave differently.

cache=none seems to be the best performance and is the default in Proxmox 2.X.

cache=directsync seems similar in performance to cache=none

cache=writethrough should help speed up reads since it can use the host disk cache for reads but in practice it performs worse than cache=none

cache=writeback should help with reads and writes at the risk of loosing data, in practice it performs worse than cache=none.

caching adds additional data copies and bus traffic causing it to perform worse.


Application Specific Tweaks

Microsoft SQL Server

Trace Flag T8038

Setting the trace flag -T8038 will drastically reduce the number of context switches when running SQL 2005 or 2008.

To change the trace flag:

  1. Open the SQL server Configuration Manager
  2. Open the properties for the SQL service typically named MSSQLSERVER
  3. Go to the advanced tab
  4. Append ;-T8038 to the end of the startup parameters option

For additional references see: Proxmox forum