here are some issues that were raised during today's LVM2 lecture, and some answers i found for them:
1. the word for "silencing" the file-system (or application) is 'quiesce'. see http://en.wikipedia.org/wiki/Quiesce for a very incomplete article. 2. Quiesce in reiserfs and ext3 - it appears there is integration between snapshot creation and quiescing the file-system. this integration is done in the kernel level as follows: before the snapshot is created, the device mapper invokes a function of the block device called "freeze_bdev". this function then will invoke a file-system specific "sync_fs" function and later a function named 'write_super_lockfs' (if the file system supports these functions). in reiserfs and ext3, this function commits any pending transactions, putting the file-system in consistent state. since this operation also blocks new I/O (until the snapshot creation was finished), we get a consistent file-system. 3. the code that implements the old RAID levels (0, 1, 5, 6) indeed does not use the new device mapper code-parts (like the dm-table). they just placed all the source files in a single directory, to confuse the reader ;) 4. when we create a read-write snapshot, and then mount the snapshot and write to it, indeed the old (frozen) data is over-written on the snapshot. there is no way to undo this, other then taking a snapshot of the snapshot. 5. when a snapshot becomes full, it is switched to 'inactive' state - it's not deleted from the system. if there were other questions which i forgot, or new questions come to mind, feel free to ask them here (or in private, if you prefer that). --guy --------------------------------------------------------------------- Haifa Linux Club Mailing List (http://www.haifux.org) To unsub send an empty message to [EMAIL PROTECTED]
