Ideally lvm2 would be used to create/manage the thin-pool volume that is
then handed to docker to exclusively create/manage the thin and thin
snapshot volumes needed for it's containers. Managing the thin-pool
outside of docker makes for the most feature-rich method of having
docker utilize device mapper thin provisioning as the backing storage
for docker's containers. lvm2-based thin-pool management feature
highlights include: automatic or interactive thin-pool resize support,
dynamically change thin-pool features, automatic thinp metadata checking
when lvm2 activates the thin-pool, etc.
Docker will not activate/deactivate the specified thin-pool device but
it will exclusively manage/create thin and thin snapshot volumes in it.
Docker will not take ownership of the specified thin-pool device unless
it has 0 data blocks used and a transaction id of 0. This should help
guard against using a thin-pool that is already in use.
Also fix typos in setupBaseImage() relative to the thin volume type of
the base image.
Docker-DCO-1.1-Signed-off-by: Mike Snitzer <snitzer@redhat.com> (github: snitm)
Commit 09ee269d ("devmapper: Add option for specifying the thin pool
blocksize") also switched the default dm-thin-pool blocksize from 64K to
512K. That change unfortunately breaks the activation of dm-thin-pool
devices that were previously created using a 64K blocksize. Here is an
example of the dm-thin-pool activation failure users may experience:
device-mapper: thin: 253:4: pool target (204800 blocks) too small: expected 1638400
device-mapper: table: 253:4: thin-pool: preresume failed, error = -22
The reason for this is docker is passing 512K as the blocksize for a
dm-thin-pool that was previously created using a 64K blocksize. Docker
doesn't record the blocksize the is used when it creates a dm-thin-pool.
Until now it never had a need to do so because the blocksize was always
hardcoded. The dm-thin-pool blocksize must be the same every time a
dm-thin-pool is activated.
As a stop-gap fix, revert to using 64K for the default blocksize.
But we do need a proper fix for this now that 'dm.blocksize' is exposed
as a proper storage option. One possible fix would be to record the
blocksize for each dm-thin-pool that docker creates and to pass that
recorded blocksize down in the dmsetup table load each time the
dm-thin-pool is activated (this would be comparable to what lvm2 does).
Docker-DCO-1.1-Signed-off-by: Mike Snitzer <snitzer@redhat.com> (github: snitm)
Add dm.blocksize option that you can use with --storage-opt to set a
specific blocksize for the thin provisioning pool.
Also change the default dm-thin-pool blocksize from 64K to 512K. This
strikes a balance between the desire to have smaller blocksize given
docker's use of snapshots versus the desire to have more performance
that comes with using a larger blocksize. But if very small files will
be used on average the user is encouraged to override this default.
Docker-DCO-1.1-Signed-off-by: Mike Snitzer <snitzer@redhat.com> (github: snitm)
The blkdiscard hack we do on container/image delete is pretty slow, but
required to restore space to the "host" root filesystem. However, it
is pretty useless on raw devices, and you may not need it in development
either.
In a simple test of the devicemapper backend on loopback the time to
delete 20 container went from 11 seconds to 0.4 seconds with
--storage-opt blkdiscard=false.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This adds dm.datadev and dm.metadatadev options that you can use with
--storage-opt to set to specific devices to use for the thin
provisioning pool.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This adds the following --storage-opts for the daemon:
dm.fs: The filesystem to use for the base image
dm.mkfsarg: Add an argument to the mkfs command for the base image
dm.mountopt: Add a mount option for devicemapper mount
Currently supported filesystems are xfs and ext4.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This allows setting these settings to be passed:
dm.basesize
dm.loopdatasize
dm.loopmetadatasize
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Mike Snitzer