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Re: RFE: mount newly formatted volumes with barrier=0



On 12/27/2010 03:41 AM, Avi Kivity wrote:
> If Anaconda has just formatted a volume, we know that there is no data 
> on that volume that can be lost.  We can therefore mount it, for the 
> duration of the installation, with barriers disabled (and make other 
> tradeoffs in the performance/integrity equation, like using 
> data=writeback for ext4).
> 
> The installed image should enable barriers as usual.
> 
> The result would be faster installation, and thus a better user experience.

If we have just formatted it, this is probably ok; I assume that
a power loss or crash during install would always result in a reinstall.

Do you have any benchmarks of an install with/without barriers?

It'd be worth testing it on a rawhide compose (do we do that still?)
because the whole barrier infrastructure has changed a lot upstream,
recently.

I'm a little less excited about other random tweaks for filesystems
such as data=writeback, since this means the installer will be using
codepaths that we don't recommend or support or test.

But it'd be interesting to see some install perf numbers for a given
kickstart file, I suppose, and for different install scenarios
(ssd, sata, virt, etc).

-Eric


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