[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Bug? qemu-img convert to preallocated image makes it sparse

From: Richard W.M. Jones
Subject: Re: Bug? qemu-img convert to preallocated image makes it sparse
Date: Thu, 16 Jan 2020 16:00:44 +0000
User-agent: Mutt/1.5.21 (2010-09-15)

On Thu, Jan 16, 2020 at 05:38:03PM +0200, Maxim Levitsky wrote:
> How about doing write zeros without discard only in this particular case 
> (convert to existing image)
> Basically omitting the BDRV_REQ_MAY_UNMAP flag to blk_co_pwrite_zeroes.
> It will be slow, but maybe for this particular case, it is acceptable?

I should probably say that we don't want to break the other case
(which is likely more important) where we write a sparse source to a
sparse target and want the target to contain only the union of the two
sparse maps, not fully allocated :-)

It would be fine, I think, to have a new "make this disk fully
allocated" operation.  qemu-img resize could almost do it with a
request to add 0 extra bytes, but the --preallocation flag only
applies to the new space.


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.

reply via email to

[Prev in Thread] Current Thread [Next in Thread]