On 03/10/2011 04:59 AM, Daniel P. Berrange wrote:
On Wed, Mar 09, 2011 at 06:45:43PM -0700, Eric Blake wrote:
POSIX states about dd:
If the bs=expr operand is specified and no conversions other than sync, noerror, or notrunc are requested, the data returned from each input block shall be written as a separate output block; if the read returns less than a full block and the sync conversion is not specified, the resulting output block shall be the same size as the input block. If the bs=expr operand is not specified, or a conversion other than sync, noerror, or notrunc is requested, the input shall be processed and collected into full-sized output blocks until the end of the input is reached.
Since we aren't using conv=sync, there is no zero-padding, but our use of bs= means that a short read results in a short write. If instead we use ibs= and obs=, then short reads are collected and dd only has to do a single write, which can make dd more efficient.
* src/qemu/qemu_monitor.c (qemuMonitorMigrateToFile): Avoid 'dd bs=', since it can cause short writes. --- src/qemu/qemu_monitor.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
ACK
Thanks; applied. -- Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org