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[Qemu-block] [PULL 04/55] docs: Document share-rw property more thorough
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PULL 04/55] docs: Document share-rw property more thoroughly |
Date: |
Tue, 13 Feb 2018 18:04:38 +0100 |
From: Fam Zheng <address@hidden>
Suggested-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Fam Zheng <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Kashyap Chamarthy <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
docs/qemu-block-drivers.texi | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/docs/qemu-block-drivers.texi b/docs/qemu-block-drivers.texi
index cd74767ed3..f1793692bb 100644
--- a/docs/qemu-block-drivers.texi
+++ b/docs/qemu-block-drivers.texi
@@ -845,6 +845,16 @@ QEMU transparently handles lock handover during shared
storage migration. For
shared virtual disk images between multiple VMs, the "share-rw" device option
should be used.
+By default, the guest has exclusive write access to its disk image. If the
+guest can safely share the disk image with other writers the @code{-device
+...,share-rw=on} parameter can be used. This is only safe if the guest is
+running software, such as a cluster file system, that coordinates disk accesses
+to avoid corruption.
+
+Note that share-rw=on only declares the guest's ability to share the disk.
+Some QEMU features, such as image file formats, require exclusive write access
+to the disk image and this is unaffected by the share-rw=on option.
+
Alternatively, locking can be fully disabled by "locking=off" block device
option. In the command line, the option is usually in the form of
"file.locking=off" as the protocol driver is normally placed as a "file" child
--
2.13.6
- [Qemu-block] [PULL 00/55] Block layer patches, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 01/55] iotests: Fix CID for VMDK afl image, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 03/55] qemu-img: Document --force-share / -U, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 02/55] qemu-img.texi: Clean up parameter list, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 09/55] gluster: Move glfs_close() to create's clean-up, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 11/55] gluster: Query current size in do_truncate(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 04/55] docs: Document share-rw property more thoroughly,
Kevin Wolf <=
- [Qemu-block] [PULL 10/55] gluster: Pull truncation from qemu_gluster_create, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 06/55] block: early check for blockers on drive-mirror, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 05/55] qcow2: Use g_try_realloc() in qcow2_expand_zero_clusters(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 08/55] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 07/55] iotests: Use virtio-blk in 155, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 15/55] sheepdog: Allow fully preallocated truncation, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 13/55] sheepdog: Make sd_prealloc() take a BDS, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 17/55] qcow2: Fix documentation of get_cluster_table(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 14/55] sheepdog: Pass old and new size to sd_prealloc(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 12/55] gluster: Add preallocated truncation, Kevin Wolf, 2018/02/13