XFS peculiar behavior

[Andi Kleen]

Yannis Klonatos <klonatos at ics.forth.gr> writes:

>         The problem is that i have noticed that XFS may - not all

Why is that a problem?

> times - split a table over a large disk distance. For
> example in one run i have noticed that a file of 13GByte is split over
> a 4,7TByte distance (I calculate this distance
> by subtracting the final block used for the file with the first
> one. The two disk blocks values are acquired using the
> FIBMAP ioctl).

I don't know if it's the only reason, but XFS does a lot of data
structure locking and updates per allocation group, so spreading
to multiple AGs gives better scalability to many CPUs.

Also I suppose it's good to avoid hot spots on the underlying 
device.

-Andi
-- 
ak at linux.intel.com -- Speaking for myself only.