Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM

[Tomasz Chmielewski]

Dietmar Maurer wrote:
> > Also, on _loaded_ systems, I noticed creating/removing logical volumes
> > can take really long (several minutes); where allocating a file of a
> > given size would just take a fraction of that.
>
> Allocating a file takes much longer, unless you use  a 'sparse' file.

If you mean "allocating" like with:

   dd if=/dev/zero of=image bs=1G count=50

Then of course, that's a lot of IO.


As you mentioned, you can create a sparse file (but then, you'll end up 
with a lot of fragmentation).

But a better way would be to use persistent preallocation (fallocate), 
instead of "traditional" dd or a sparse file.


--
Tomasz Chmielewski
http://wpkg.org