From: Greg Farnum Date: Mon, 1 Nov 2021 23:36:47 +0000 (+0000) Subject: doc: fix up rbd snapshot docs around crash consistency X-Git-Tag: v17.1.0~404^2 X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=1903ce28a979beba4d496cf139c2825a6d132e20;p=ceph.git doc: fix up rbd snapshot docs around crash consistency Signed-off-by: Greg Farnum --- diff --git a/doc/rbd/rbd-snapshot.rst b/doc/rbd/rbd-snapshot.rst index 701acec2f3a..96dec81c87c 100644 --- a/doc/rbd/rbd-snapshot.rst +++ b/doc/rbd/rbd-snapshot.rst @@ -15,13 +15,13 @@ VM image) quickly and easily. Ceph block device snapshots are managed using the .. important:: To use RBD snapshots, you must have a running Ceph cluster. .. note:: Because RBD does not know about any filesystem within an image - (volume), snapshots are not `crash-consistent` unless they are + (volume), snapshots are only `crash-consistent` unless they are coordinated within the mounting (attaching) operating system. We therefore recommend that you pause or stop I/O before taking a snapshot. - If the volume contains a filesystem, it must be in an internally - consistent state before taking a snapshot. Snapshots taken at - inconsistent points may need a `fsck` pass before subsequent - mounting. To stop `I/O` you can use `fsfreeze` command. See + If the volume contains a filesystem, it should be in an internally + consistent state before taking a snapshot. Snapshots taken without + write quiescing may need an `fsck` pass before subsequent + mounting. To quiesce `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 file systems when creating a snapshot.