Commit eb461485 authored by Fam Zheng's avatar Fam Zheng Committed by Kevin Wolf
Browse files

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: default avatarKevin Wolf <kwolf@redhat.com>
Signed-off-by: default avatarFam Zheng <famz@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 2f9d4083

qemu-img.texi

+4 −2
Original line number Diff line number Diff line
@@ -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