[libvirt] [PATCHv3] qemu: reduce file padding requirements

[Laine Stump]

On 06/10/2010 03:31 PM, Eric Blake wrote:
> Followup to https://bugzilla.redhat.com/show_bug.cgi?id=599091,
> commit 20206a4b, to reduce disk waste in padding.
>
> * src/qemu/qemu_monitor.h (QEMU_MONITOR_MIGRATE_TO_FILE_BS): Drop
> back to 512.
> (QEMU_MONITOR_MIGRATE_TO_FILE_TRANSFER_SIZE): New macro.
> * src/qemu/qemu_driver.c (qemudDomainSaveFlag): Update comment.
> * src/qemu/qemu_monitor_text.c (qemuMonitorTextMigrateToFile): Use
> two invocations of dd to output non-aligned large blocks.
> * src/qemu/qemu_monitor_json.c (qemuMonitorJSONMigrateToFile):
> Likewise.
> ---
>
> v2: avoid truncating regular file destination
>
> v3: change minimum block size from 512 to 4k, to avoid unaligned
> RMW cycles on newer disks with 4k sectors
>    

Okay, I've finally gotten around to trying this out, and in addition to 
reducing the file size, it also works!

ACK

(Note: I haven't tested saving to a block device, so I'm taking the word 
of the dd documentation that this works as well ;-)