On 14/05/2007, at 2:59 PM, David Lloyd wrote:
Phil,
sudden drop out. I guess another good idea is to protect with a
UPS of some sort - they are relatively cheap (compared to losing
all the data) and only need offer a minute or 2 up time to be able
to unmount the partition correctly and shutdown.
True; I wonder whether there's been any serious study done on what
common file systems actually "do" when the power just goes out from
underneath them.
That was one of the points of softupdates on FreeBSD. FreeBSD's
default filesystem (UFS2) does not have journalling; instead it uses
softupdates which writes metadata using an ordering method which
guarantees a consistent filesystem when a crash or power failure occurs.
As an interesting aside, journalling has been available since mid
last year, but the filesystem itself is not journalled. Journalling
is provided through a disk transformation framework called "geom".
The "gjournal" class consumes two providers - one for data and one as
a journal, and combines them to expose a journalled device.
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