From c36d73eedb70c3ce2c994b8ab6aabb558983b4bc Mon Sep 17 00:00:00 2001 From: Nilamdyuti Goswami Date: Sun, 13 Dec 2015 01:23:30 +0530 Subject: [PATCH] doc: Modified a note section in rbd-snapshot doc. Elaborates the note section a bit more as to why stopping I/O before taking a snapshot is recommended and how to do it. Signed-off-by: Nilamdyuti Goswami --- doc/rbd/rbd-snapshot.rst | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/doc/rbd/rbd-snapshot.rst b/doc/rbd/rbd-snapshot.rst index 96169efa51969..2e5af9f181f7e 100644 --- a/doc/rbd/rbd-snapshot.rst +++ b/doc/rbd/rbd-snapshot.rst @@ -14,9 +14,14 @@ command and many higher level interfaces, including `QEMU`_, `libvirt`_, .. important:: To use use RBD snapshots, you must have a running Ceph cluster. -.. note:: **STOP I/O BEFORE** snapshotting an image. - If the image contains a filesystem, the filesystem must be in a - consistent state **BEFORE** snapshotting. +.. note:: If a snapshot is taken while `I/O` is still in progress in a image, the + snapshot might not get the exact or latest data of the image and the snapshot + may have to be cloned to a new image to be mountable. So, we recommend to stop + `I/O` before taking a snapshot of an image. If the image contains a filesystem, + the filesystem must be in a consistent state before taking a snapshot. To stop + `I/O` you can use `fsfreeze` command. See `fsfreeze(8)` man page for more details. + For virtual machines, `qemu-guest-agent` can be used to automatically freeze + filesystems when creating a snapshot. .. ditaa:: +------------+ +-------------+ | {s} | | {s} c999 | -- 2.39.5