Re: Possible to use multiple disk to bypass I/O wait?

[Gordon Messmer <yinyang@xxxxxxxxx>]

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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