Hi,
On Wed, 9 Feb 2000 21:15:14 +0000 (GMT), Riley Williams
<rhw@MemAlpha.CX> said:
>> No. Ext3 is currently fully backwards compatible with ext2.
> From experience, no it isn't. However, I think what you meant to
> say was that the ext3 driver is fully capable of reading ext2 file
> systems, in which case you are of course right.
That's what backwards compatibility _means_.
>> Once you unmount an ext3 filesystem cleanly, the journal bit is
>> cleared, and a standard ext2 filesystem code and standard ext2
>> utilities will work just fine with the filesystem.
> First, your use of the word "cleanly" invalidates your claim that it's
> backwards compatible since the latter claim is meaningless unless it's
> true with unclean unmounts.
No --- ext2 can't arbitrarily read ext3 filesystems. That would imply
*forwards* compatibility, which has never been claimed. ext3 can leave
a filesystem in a state ext2 can deal with if you unmount cleanly,
allowing you to migrate between ext2 and ext3 easily, but ext2 simply
cannot be allowed to read and write uncleanly-unmounted ext3 filesystems
without first forcing the ext3 journal to be recovered (that would just
invite completely unnecessary filesystem corruption).
> My memory may be wrong here, but it seems to remember SCT stating that
> he chose to rename to ext3 since the journalling facility was likely
> to make the driver not be backwards compatible with the current code.
> SCT: Am I wrong here?
Yes! It was chosen to keep the new codebase separate from the old,
trusted ext2 code.
--Stephen
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