Hi, I have a running gmirror. Somewhere in its docs there is a mentioning about writing meta data to the last sector of a disk. Now, I would like to add PJD's gjournal journaling on top of the mirror. As far as I understand, it does write some meta data to the last sector of the journaled device, too. Will it overwrite the gmirror meta data and thus break the mirror or will it somehow magically work? Does each GEOM layer make the resulting block device one sector shorter? -- Vaclav Haisman -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 542 bytes Desc: OpenPGP digital signature Url : http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20060809/1596dcc9/signature.pgp
V?clav Haisman wrote:> journaled device, too. Will it overwrite the gmirror meta data and thus > break the mirror or will it somehow magically work? Does each GEOM layer > make the resulting block device one sector shorter?No, when you create a mirror device, its size will be one sector less than size_of_raw_device. So when you add another GEOM class in it, the "last sector" will be the one before the last on the physical provider, and the new size will be two sectors less than physical, etc. In other words, geoms are "nesting" in each other and each nested geom is one sector smaller than the one it's in.