On 06/09/2011 08:21 PM, Emmanuel Noobadmin wrote:
But now that you brought it up, I'm wondering if that would had been
pointless. If the kernel considers KVM opening the diskfile and
holding onto it as a single access, regardless of how many subsequent
reads/writes there are, then this wouldn't make a difference would it?
atime and mtime are updated for *every* read and write operation, not
for the open() of the file.

That aside, if you're running KVM I strongly recommend using LVM rather
than file-backed VM guests. It's more work to set up, but you'll see
drastically better IO performance in the guests. One system that I
measured had a write speed of around 8 MB/s for sequential block output
on file-backed VMs. LVM backed VMs wrote at around 56 MB/s for
sequential block output.

You should *never* used file-backed VMs for production systems.

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postedJun 9, '11 at 5:24a
activeJun 16, '11 at 4:01a



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