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[Qemu-devel] [Bug 568445] Re: LVM backed drives should default to cache=
[Qemu-devel] [Bug 568445] Re: LVM backed drives should default to cache='none'
Sat, 14 Aug 2010 01:22:08 -0000
cache=writethrough and cache=none have equivalent data integrity.
FWIW, I believe most recent versions of virt-manager default to
cache=none for physical devices.
LVM backed drives should default to cache='none'
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Status in QEMU: Invalid
Status in “virt-manager” package in Ubuntu: Triaged
Binary package hint: virt-manager
KVM guests using LVM backed drives appear to experience fairly high iowait
times on the host system if the guest has even a moderate amount of disk I/O.
This translates to poor performance for the host and all guests running on the
host, and appears to be due to caching as KVM defaults to using writethrough
caching when nothing is specified. Explicitly disabling KVM's caching appears
to result in significantly better host and guest performance.
This is recommended in at least a few places: