On Tue, Apr 21, 2015 at 7:33 AM, Andrew Berg <aberg010 at my.hennepintech.edu> wrote: > See the zpool-features man page. It varies by feature. Some will completely > prevent import in this case, while others may simply only make the pool > read-only. Also, some features are not mandatory at upgrade time and will not > be enabled automatically. If a feature is disabled, support for it is not > required for import. This is a bit misleading, as the feature would need to have been disabled from the start. Lets say i create a feature of supercompressor which compresses everything with my super secret proprietary algorithm(so secret that even decrypting is a closely held secret), disabling this feature only affect NEW blocks and old blocks will remain compressed with this proprietary compressor rendering the pool unimportable by a ZFS implementation that does not understand the supercompressor feature flag.