Re: Lost file-system story

[Donald Allen <donaldcallen%gmail.com@localhost>]

On Wed, Dec 7, 2011 at 9:58 AM, Ignatios Souvatzis 
<presse%ycm-bonn.de@localhost> wrote:
> On Tue, Dec 06, 2011 at 12:44:16PM -0500, Donald Allen wrote:
>> On Tue, Dec 6, 2011 at 11:58 AM, Thor Lancelot Simon 
>> <tls%panix.com@localhost> wrote:
>> > On Tue, Dec 06, 2011 at 11:10:44AM -0500, Donald Allen wrote:
>> >>
>> >> 2. I'm a little bit surprised that the filesystem was as much of a
>> >> mess as it was.
>> >
>> > I'm not.  You mounted the filesystem async and had a crash.  With the
>> > filesystem mounted async *nothing* pushes out most metadata updates,
>> > with the result that the filesystem's metadata can quickly enter a
>> > fatally inconsistent state.  The only way home safe is a clean unmount.
>>
>> So unwritten meta-data from an async filesystem can sit in the buffer
>> cache for arbitrarily long periods of time in NetBSD? I just want to
>> be sure I understand what you are saying. Because that essentially
>> guarantees, as you imply above, that if the system crashes, you will
>> lose the filesystem. That makes the following warning, in the mount(8)
>> man page, in the description of the async option:
>>
>> "In the event of a crash, it is impossible for the system to verify
>> the integrity of data on a file system mounted with this option."
>>
>> much more clear. When I read this before the fun started, I took it to
>
> You left out part of the warning. From NetBSD 5.1:
>
>   async       All I/O to the file system should be done asyn-
>               chronously.  In the event of a crash, it is
>               impossible for the system to verify the integrity of
>               data on a file system mounted with this option.  You
>               should only use this option if you have an applica-
>               tion-specific data recovery mechanism, or are willing
>               to recreate the file system from scratch.
>
> Isn't the last sentence of that paragraph in your version?

No. My version says "If you use this option and the system crashes,
everything will be fine."

/Don