>>>>> "cb" == C Bergström <cbergst...@netsyncro.com> writes:
cb> ideas for good zfs GSoC projects, but wanted to stir some
cb> interest.
Read-only vdev support.
1. possibility to import a zpool on DVD. All filesystems within would
be read-only. DVD should be scrubbable: result would be a list of
files with defects.
2. possible to import a zpool of writeable devices as ``read-mostly''.
All filesystems within it would be read-only, but you could still
scrub it, and future ``vdev shrink'' features would work on it, and
the existing silent-fsck features like label rewriting or ZIL
rolling or whatever would occur. This would be used for creating
the DVD master images above.
3. possible to add a read-write vdev to the read-only zpool, and make
the zpool become read-write.
4. (maybe) possible to import zpool as non-persistent. All writes
would be stored in ARC/L2ARC, and the max size of writes could be
capped.
use cases:
0. mounting other machines' pools without rewriting labels
1. live CD's (obvious),
2. SOX compliant backups, when backups must be done to WORM media.
you import several read-only vdev's and keep attaching one
read-write vdev to the ``end'' of the pool when you want to add a
blob of data. the first and each successive vdev becomes full,
incremental, incremental, incremental---thus replication and
backup converge.
Through (2) ``read-mostly'' import with bp-rewrite it's possible
to condense vdev's, for example to coalesce fifteen WORM daily
incrementals whose write fuse has already blown, into a single new
big vdev, and then detach the fifteen tiny ones.
A variety of apparent pools are importable depending on what
combination of vdev's you would like to use. 'zpool import' would
have to become a bit more complicated, to list the workable
combinations and mask unwanted devices as you order it.
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