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authorFam Zheng <famz@redhat.com>2018-07-11 09:22:27 +0800
committerKevin Wolf <kwolf@redhat.com>2018-07-12 18:24:08 +0200
commiteb461485f4558e362fab905735b50987505bca44 (patch)
treea28f9385d40bf1efc1f35491a7a09332cc98e900 /qemu-img.texi
parent2f9d4083f7fdafe82138e983a24ef30b81b029d7 (diff)
qemu-img: Document copy offloading implications with -S and -c
Explicitly enabling zero detection or compression suppresses copy offloading during convert. Document it. Suggested-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'qemu-img.texi')
-rw-r--r--qemu-img.texi6
1 files changed, 4 insertions, 2 deletions
diff --git a/qemu-img.texi b/qemu-img.texi
index aeb1b9e66c..5853cd18d1 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -96,7 +96,8 @@ will enumerate information about backing files in a disk image chain. Refer
below for further description.
@item -c
-indicates that target image must be compressed (qcow format only)
+indicates that target image must be compressed (qcow format only). If this
+option is used, copy offloading will not be attempted.
@item -h
with or without a command shows help and lists the supported formats
@@ -115,7 +116,8 @@ in case both @var{-q} and @var{-p} options are used.
indicates the consecutive number of bytes that must contain only zeros
for qemu-img to create a sparse image during conversion. This value is rounded
down to the nearest 512 bytes. You may use the common size suffixes like
-@code{k} for kilobytes.
+@code{k} for kilobytes. If this option is used, copy offloading will not be
+attempted.
@item -t @var{cache}
specifies the cache mode that should be used with the (destination) file. See