[Libguestfs] [PATCH] New tool: virt-format

[Paolo Bonzini]

On 01/17/2012 07:11 PM, Richard W.M. Jones wrote:
> >  - does it align partitions to SSD erase block size? (LVM is
> >      particularly tricky to get right manually)
>
> It aligns to 64K at the moment, for partitions.  For LVM we just use
> the defaults, whatever they are.  I don't know if it is possible to
> pass the SSD erase block size up through the virt stack.
>
> CC'd to Paolo Bonzini: Will virtio-scsi make this easier for us in
> future?

SSD erase data will be passed up transparently if you pass the entire 
disk to the VM.  Otherwise, it will make this a bit easier (there will 
be no changes required to the guest, only the host) but some code has to 
be written to get the info from sysfs.

>>  - can --wipe use TRIM on SSDs instead of writing zeroes?
>
> Paolo Bonzini: ^^ same question about virtio-scsi ^^

Same here: no changes required to the guest, only the host.  You will 
also be able to punch holes in image files when TRIM commands are issued 
to the SCSI disk, and the image files will become sparse as long as the 
underlying file systems supports that.

Paolo