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author | Fam Zheng <famz@redhat.com> | 2018-02-09 13:29:15 +0800 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2018-02-13 12:27:17 +0100 |
commit | c1a4b6f9246bf2841b14b11d4c5a029429f0659a (patch) | |
tree | 765a4eb198326bd2558267aeaf4b9a08a129cf21 /docs/qemu-block-drivers.texi | |
parent | a7e326df1c116e99e6e65ca02c6eadb5bd5aef45 (diff) | |
download | qemu-c1a4b6f9246bf2841b14b11d4c5a029429f0659a.zip qemu-c1a4b6f9246bf2841b14b11d4c5a029429f0659a.tar.gz qemu-c1a4b6f9246bf2841b14b11d4c5a029429f0659a.tar.bz2 |
docs: Document share-rw property more thoroughly
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'docs/qemu-block-drivers.texi')
-rw-r--r-- | docs/qemu-block-drivers.texi | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/docs/qemu-block-drivers.texi b/docs/qemu-block-drivers.texi index cd74767..f179369 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 |