On Mon, Jan 31, 2005 at 11:25:52AM -0800, Jason Thorpe wrote: > The issue is that the FFS code in these kernels needs to be aware of > snapshots that may already exist on the file systems. Hm, so there's some new on-disk format the new kernel must recognise - though perhaps only if I've actually created a snapshot? What are the consequences if the kernel doesn't recognise this new format? What if I boot an older kernel on this machine? As we saw with the superblock upgrade issues, that happens more often that we might expect, though this time hopefully it only affects people actually making snapshots. If the consequences are nasty, should we do something like raise the FFS version number on disk, once snapshots have been created, if there's no other way to make these filesystems safe from older kernels? Space issues aside, having snapshots in INSTALL kernels could be _very_ useful for those using snapshots and iso's to upgrade systems (which is the only time the compatibility question will arise, of course). Not that it should be a substitute for a proper backup before the upgrade, but lets face it, many people won't do one. Teaching sysinst to offer the option of making such a snapshot before upgrading would be a seriously useful end-user feature. Now, how do I actually use internal snapshots? I know about fss(4), but haven't come across docs for the latter. -- Dan.
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