On Tuesday 16 January 2007 4:23 am, Daniele Palumbo wrote:
> but, which is the difference between that approach with "w!" (saying that
> all domU's will mount only ro) and the above?
"w!" tells to the Xen device handling not to check anything, in case you want
to use a cluster FS (ocfs2 or GFS). both "r" and "w" check that you're safe
to use 'normal' filesystems. a "r!" as you wish would allow one rw and
several ro; something that is not supported by any non-cluster filesystem.
i think you beleive that somehow making an exception for Dom0, letting it
write 'sometimes' is still 'almost safe'. it is not.
> domU's will became unstable (strange, i figured out only files missing, as
> i think it should be) in the same way, and also (saying that i have "bad
> guys playing with my domUs) i can have a data loss.
all FS i know about (except maybe FAT, of course) might do complex and
sophisticated things with the directory structures any time you write. (some
of them reshuffle file data too). for example, ext3 keeps the directory
sorted and changes from a linear list to an htree after a given threshold.
> so, again, why is not "r!" a valid flag?
because it doesn't make any sense. "r" and "w" are 'safe', "w!" is safe too
if you know what you're doing (cluster FS); "r!" as you wish wouldn't be safe
for any non-cluster FS, and useless for cluster FSs
--
Javier
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