Date: Thu, 1 Jul 2004 16:22:43 +1000 From: Q <q_dolan@yahoo.com.au> To: Sam Lawrance <boris@brooknet.com.au> Cc: freebsd-hackers@freebsd.org Subject: Re: writing to RW-mounted UFS2 snapshots - confirmed. Message-ID: <0FAC476E-CB27-11D8-9145-000D9335C6A0@yahoo.com.au> In-Reply-To: <1088648757.56400.5.camel@dirk> References: <20040630115340.L806-100000@kozubik.com> <1088648757.56400.5.camel@dirk>
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On 01/07/2004, at 12:25 PM, Sam Lawrance wrote:
>> This is unexpected. You can successfully mount the snapshot
>> read/write and create and write to files in that snapshot. You can
>> also write to files that existed in the snapshot prior to mounting it
>> read/write.
>
> Perhaps the writing is done from a point where the schg flag is not
> checked or obeyed?
While this may not be "expected" behavior, I am curious why this is
something that should be prevented, rather than verified for
correctness? By "correct" I mean, that the copy on write process is
performed correctly and modifications made to the snapshot don't modify
the underlying filesystem elements also.
To me this has the potential to allow snapshots to be used in reverse
as a sort of an "undo drive", similar to unionfs, where you can make
changes to a snapshot without the changes being permanently applied to
the live filesystem. This might be useful for testing an upgrade or
database recovery on a "staging" snapshot before attempting to modify
the real thing.
--
Seeya...Q
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
_____ / Quinton Dolan - q_dolan@yahoo.com.au
__ __/ / / __/ / /
/ __ / _/ / / Gold Coast, QLD, Australia
__/ __/ __/ ____/ / - / Ph: +61 419 729 806
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