From d5c1bab6fdc143193345d7d1d73533ad45e10b1a Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Sun, 26 Nov 2017 14:32:26 +0100 Subject: [PATCH] ganeti: add a section about disk cache configuration --- input/howto/install-ganeti.creole | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/input/howto/install-ganeti.creole b/input/howto/install-ganeti.creole index 2f21981..d88f024 100644 --- a/input/howto/install-ganeti.creole +++ b/input/howto/install-ganeti.creole @@ -483,6 +483,16 @@ both the network and disk speed allow that. }}} +=== Change the disk cache === + +When using raw volumes or partitions, it is best to avoid the host cache completely to reduce data copies +and bus traffic. This can be done using: + +{{{ + gnt-cluster modify -H kvm:disk_cache=none +}}} + + === Change the CPU type === Modern processors come with a wide variety of additional instruction sets (SSE, AES-NI, etc.) which vary from processor to processor, but can greatly improve the performance depending on the workload. Ganeti and QEMU default to a compatible subset of cpu features called qemu64, so that if the host processor is changed, or a live migration is performed, the guest will see its CPUfeatures unchanged. This is great for compatibility but comes at a performance cost. -- 2.20.1