From a22f123ca3d3c09a77af4341ed1fbcc175b54f1d Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 26 Aug 2011 15:27:13 +0200 Subject: qemu-img: Require larger zero areas for sparse handling By default, require 4k of consecutive zero bytes for qemu-img to make the output file sparse by not issuing a write request for the zeroed parts. Add an -S option to allow users to tune this setting. This helps to avoid situations where a lot of zero sectors and data sectors are mixed and qemu-img tended to issue many tiny 512 byte writes. Signed-off-by: Kevin Wolf --- qemu-img.texi | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'qemu-img.texi') diff --git a/qemu-img.texi b/qemu-img.texi index 495a1b6695..70fa321dff 100644 --- a/qemu-img.texi +++ b/qemu-img.texi @@ -40,6 +40,11 @@ indicates that target image must be compressed (qcow format only) with or without a command shows help and lists the supported formats @item -p display progress bar (convert and rebase commands only) +@item -S @var{size} +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. @end table Parameters to snapshot subcommand: @@ -86,7 +91,7 @@ it doesn't need to be specified separately in this case. Commit the changes recorded in @var{filename} in its base image. -@item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] @var{filename} [@var{filename2} [...]] @var{output_filename} +@item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename} Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename} using format @var{output_fmt}. It can be optionally compressed (@code{-c} -- cgit v1.2.1