Re: xfs_growfs / planned resize / performance impact

[Stefan Priebe - Profihost AG <s.priebe@xxxxxxxxxxxx>]

Am 03.08.2012 06:03, schrieb Eric Sandeen:
> On 7/31/12 8:56 AM, 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.
> >
> > Should i take care of that and format these disks with special parameters?
> >
> > I've discovered that a 500GB volume has agcount=4 and 64000 blocks of internal 
> > log - while a 300GB volume resized to 500GB has agcount 7 ad only 40960 blocks 
> > of internal log.
> >
> > Is it a problem if this grow will happen in small portions (30GB => 50GB => 75GB 
> > => 100GB => ... 300GB)?
> This incremental part doesn't matter a bit.  The first mkfs will choose the AG 
> count & size according to defaults;
> further growth after this will add new (possibly partial) AGs of that 
pre-chosen size.
OK thanks for your reply. But does this influence performance? Should i 
perhaps start creating the 30GB with agcount 1 so that while raising the 
disk i don't end up with such a high agcount value? Does it make sense 
to create a bigger internal log from he beginning?
Thanks

Stefan