Performance impact of mkfs.xfs vs mkfs.xfs -f

[Dave Chinner]

On Wed, Aug 26, 2015 at 02:39:11AM +0200, Carlos E. R. wrote:
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> On 2015-08-26 01:43, Dave Chinner wrote:
> > On Tue, Aug 25, 2015 at 04:09:33PM -0700, Shrinand Javadekar 
> > wrote:
> 
> >> Formatted the new disks with mkfs.xfs. Ran the workload. 
> >> Reformatted the disks with mkfs.xfs -f. Ran the workload.
> 
> 
> > Anyway, please post the output so we can see the differences for 
> > ourselves. What we need is mkfs output in both cases, and xfs_info
> >  output in both cases after mount.
> 
> Suggestion (for the OP):
> 
> To reformat a third time without "-f", you can reformat as ext4, then
> format a second time as xfs.

That doesn't work - mkfs.xfs detects that the device has an ext4
filesystem on it, and demands you use -f to overwrite it.

> But to imitate a new disk, you have to
> zero it with dd.

Only the first MB or so - enough for blkid not to be able to see a
filesystem signature on it.

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com