Difference between revisions of "Performance Tweaks"
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cache=none seems to be the best performance and is the default in Proxmox 2.X. | cache=none seems to be the best performance and is the default in Proxmox 2.X. | ||
| + | host don't do cache. | ||
| + | Similar to writeback, but host don't do cache | ||
| + | guest disk cache is writeback | ||
| + | Warn : like writeback, you can loose datas in case of a powerfailure | ||
| + | you need to use barrier option in your linux guest fstab if kernel < 2.6.37 to avoid fs corruption in case of powerfailure. | ||
| + | |||
| + | cache=writethrough | ||
| + | host do read cache | ||
| + | guest disk cache mode is writethrough | ||
| + | Writethrough make a fsync for each write. So it's the more secure cache mode, you can't loose data. It's also the slower. | ||
| + | Writethrough enable read cache on host. | ||
| − | cache=directsync | + | cache=directsync. |
| + | host don't do cache. | ||
| + | guest disk cache mode is writethrough | ||
| + | similar to writethrough, a fsync is made for each write. | ||
| + | |||
| − | cache= | + | cache=writeback |
| − | + | host do read/write cache | |
| − | cache | + | guest disk cache mode is writeback |
| + | Warn : you can loose datas in case of a powerfailure | ||
| + | you need to use barrier option in your linux guest fstab if kernel < 2.6.37 to avoid fs corruption in case of powerfailure. | ||
| + | |||
caching adds additional data copies and bus traffic causing it to perform worse. | caching adds additional data copies and bus traffic causing it to perform worse. | ||
| − | |||
=Application Specific Tweaks= | =Application Specific Tweaks= | ||
Revision as of 13:52, 19 September 2012
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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
USB Tablet Device
Disabling the USB tablet device in windows VMs can reduce idle CPU usage and reduce context switches. [1]
VirtIO
Use virtIO for disk and network for best performance.
Linux has the drivers built in
Windows requires drivers which can be obtained here: Fedora VirtIO Drivers
Disk Cache
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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.
host don't do cache.
Similar to writeback, but host don't do cache
guest disk cache is writeback
Warn : like writeback, you can loose datas in case of a powerfailure
you need to use barrier option in your linux guest fstab if kernel < 2.6.37 to avoid fs corruption in case of powerfailure.
cache=writethrough
host do read cache
guest disk cache mode is writethrough
Writethrough make a fsync for each write. So it's the more secure cache mode, you can't loose data. It's also the slower.
Writethrough enable read cache on host.
cache=directsync.
host don't do cache.
guest disk cache mode is writethrough
similar to writethrough, a fsync is made for each write.
cache=writeback
host do read/write cache
guest disk cache mode is writeback
Warn : you can loose datas in case of a powerfailure
you need to use barrier option in your linux guest fstab if kernel < 2.6.37 to avoid fs corruption in case of powerfailure.
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:
- Open the SQL server Configuration Manager
- Open the properties for the SQL service typically named MSSQLSERVER
- Go to the advanced tab
- Append ;-T8038 to the end of the startup parameters option
For additional references see: Proxmox forum