Yes, but...
> I noted
> that the "make new partition and copy" method requires, first off, space
> for a new partition. All my partitions have massive amount of data on them.
> I can't do that. Those of us that can have to either do it twice, or rewrite
> fstab.
Rewriting fstab shouldn't be a problem :-).
> Eventually I'm hoping it can be done on a read-write filesystem. It's
> possible; I've thought about how to defragment read-write datasystems
> without getting in the way of logical operations.
Seriously, though, I was thinking more of what's most useful in a
server situation, where it's not uncommon to have a lot of spare
capacity - I don't think that the kernel mode read-only only converter
is going to be much of an advantage over a userspace solution in those
situations, whereas a read-write one would potentially be, because
although it's reasonable to expect backups to be done anyway, if you
can avoid the downtime needed for the restore, that's a Good Thing.
> >What I'd like to see is union mounts which allowed you to mount a new
> >filesystem of a different type over the original one, and have all new
> >writes go to the new fileystem. I.E. as files were modified, they
> >would be re-written to the new FS. That would be one way of avoiding
> >the performance hit on a busy server.
> >
>
> mmmm, then you'd need both fs' though. That's not conversion ;-)
The idea was to transparently delete files from the old filesystem
once they had been written to, and therefore transferred to the new
filesystem.
I think you've missed my point - for a desktop machine, an hour or two
downtime is usually no problem. For an ISPs webserver, it usually
is, (unless there are a cluster of them serving requests for the same
sites). However, to be able to convert filesystems without:
* Significant performance loss of network serving applications
* Significant downtime
is a very desireable feature, but the ability to do this on a
read-write filesystem is critical - if it has to be unmounted, it's
not as useful.
The reason I mentioned union mounts was because BSD already has union
mounts - see the mount_union manual page for more details. I don't
know of an implementation that allows you to automatically delete the
file on the old filesystem, when the copy on the new filesystem has
been made, though.
John.
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