Re: Journalling filesystems

[Marco Gerards]

Marcus Brinkmann <marcus.brinkmann@ruhr-uni-bochum.de> writes:

>> Not just for a server OS.  Any OS would get rock solid from it.  The problem
>> that a crashing computer kills your installation is only partly gone with
>> journalling as in ext3.  With transactions there is no way a crash can 
>> destroy
>> the system, not even if it happens during an upgrade of critical components.
>> Unless the crash is in the hardware, notably the hard disk, of course.
>
> Of course, this is not only an OS issue, but also an application
> issue.  As was correctly pointed out, the application needs to provide
> hints when a transaction starts and ends.
>
> This is very powerful, but also has drawbacks (performance, apps need
> to change).  Anyway, things like this is what the Hurd design wants to
> make easy to add in userspace, so go for it.

The main problem to consider here is how to prevent the journal to get
filled too quickly.  Consider a 1GB file which you drastically change.
That means you will have a 1GB transaction.  Normally a journal is a
lot smaller.

--
Marco