xfs_growfs / planned resize / performance impact

[Dave Chinner]

On Sun, Aug 05, 2012 at 07:46:33AM +0200, Stefan Priebe wrote:
> Am 05.08.2012 um 00:43 schrieb Dave Chinner <david at fromorbit.com>:
> 
> > On Tue, Jul 31, 2012 at 03:56:54PM +0200, Stefan Priebe - Profihost AG wrote:
> >> Hello list,
> >> 
> >> i'm planning to create a couple of VMs with just 30GB of space while
> >> using xfs as the main filesystem.
> >> 
> >> Now i alreay know that some of the VMs will grow up to 250GB while
> >> resizing the block device and using xfs_growfs.
> > 
> > Just use thin provisioning and make it 250GB to begin with. Thin
> > provisioning mades filsystem grow/shrink pretty much redundant....
> 
> But dm thin isn't stable isn't it?

AFAIK, It's mostly stable.

> Does xfs reallocate used parts of the block
> Device before using new parts?

Sometimes. Depends on workload, locality of reference,  patterns of
freeing and allocation, etc.

> Otherwise deleting and recreating files will result in full used space pretty fast.

fstrim. dm-thinp supports discard commands just fine.

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com