[PVE-User] Image format of disc
daniel at rimspace.net
Thu May 20 15:15:49 CEST 2010
"Erik van Ast" <Erik.van.Ast at suzohapp.nl> writes:
> Can someone tell me what kind of image format we should use when creating
> new VM's? We have 2 VM's running at the moment. One is using VMDK because I
> copied it from a VMWARE ESX server, and the other is in RAW format because I
> also created a new VM and RAS is the default setting. Which one is
> considered best and most reliable?
Heh. This is relevant to me next question, so let me answer this bit on the
Generally, raw is the best performing option, and is preferable if you can
allocate a block of disk storage (eg: an LV) to the system.
QCOW2 is the best choice if you want a file sitting on top of a file-system,
for some reason.
Meanwhile, my question was specifically about performance: ideally, I would
like to have my KVM systems configured with raw storage backed by an LV, and
with the 'cache=none' option passed to the kvm binary.
That allows the kernel to bypass copies of the data, and the host cache, which
given that I have allocated almost all memory to the KVM guest, is what I
actually want to happen.
Is it possible to tune these fine details along with the gross storage format
✣ Daniel Pittman ✉ daniel at rimspace.net ☎ +61 401 155 707
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